A064538 -id:A064538 - cp's OEIS frontend

A079618 Triangle of coefficients in polynomials for partial sums of powers, scaled to produce integers: Sum_{i=1..m} i^(n-1) = Sum_{k=1..n} T(n,k)*m^k/A064538(n-1).

1, 1, 1, 1, 3, 2, 0, 1, 2, 1, -1, 0, 10, 15, 6, 0, -1, 0, 5, 6, 2, 1, 0, -7, 0, 21, 21, 6, 0, 2, 0, -7, 0, 14, 12, 3, -3, 0, 20, 0, -42, 0, 60, 45, 10, 0, -3, 0, 10, 0, -14, 0, 15, 10, 2, 5, 0, -33, 0, 66, 0, -66, 0, 55, 33, 6, 0, 10, 0, -33, 0, 44, 0, -33, 0, 22, 12, 2, -691, 0, 4550, 0, -9009, 0, 8580, 0, -5005, 0, 2730, 1365, 210

Offset: 1

Henry Bottomley, Jan 29 2003

Rosinger connects this sequence to Weisstein's Faulhaber's Formula page. Rosinger also discusses, without reference to OEIS, (1.1) A000217 Triangular numbers: a(n) = C(n+1,2) = n*(n+1)/2 = 0+1+2+...+n; (1.2) A000330 Square pyramidal numbers: 0^2+1^2+2^2+...+n^2 = n*(n+1)*(2n+1)/6; (1.4) A033312 n! - 1 [with different offset and the formula 1*1! + 2*2! + 3*3! + ...]; (1.4) A007489 Sum_{k=1..n} k!. - Jonathan Vos Post, Feb 22 2007

			Triangle T(n, k) begins:
n\k 1   2   3   4   5    6   7   8   9 10 ...
1:  1
2:  1   1
3:  1   3   2
4:  0   1   2   1
5: -1   0  10  15   6
6:  0  -1   0   5   6    2
7:  1   0  -7   0  21   21   6
8:  0   2   0  -7   0   14  12   3
9: -3   0  20   0 -42    0  60  45  10
10: 0  -3   0  10   0  -14   0  15  10  2
... Reformatted. - _Wolfdieter Lang_, Feb 02 2015
For example row n=7: partial sums of 6th powers (A000540)
  1^6+2^6+...+m^6 = (m-7*m^3+21*m^5+21*m^6+6*m^7)/42.

Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, p. 106, 1996.

R. Mestrovic, A congruence modulo n^3 involving two consecutive sums of powers and its applications, arXiv:1211.4570 [math.NT], 2012. - From _N. J. A. Sloane_, Jan 03 2013
R. Mestrovic, On a Congruence Modulo n^3 Involving Two Consecutive Sums of Powers, Journal of Integer Sequences, Vol. 17 (2014), 14.8.4.
Elemer E. Rosinger, Synthesizing Sums, arXiv:math/0702605 [math.GM], 2007.
Eric Weisstein's World of Mathematics, Power Sum
Eric Weisstein's World of Mathematics, Faulhaber's Formula.

Cf. A064538, A000217, A000330, A007489, A033312.

T := proc(n, k) option remember; local A, B;
A := proc(n) option remember; denom((bernoulli(n+1,x)-bernoulli(n+1))/(n+1)) end:
B := proc(n) option remember; add(T(n,j),j=2..n) end;
if k>1 then T(n-1,k-1)*(n-1)*A(n-1)/(k*A(n-2)) elif n>1 then A(n-1)-B(n) else 1 fi end: seq(print(seq(T(n,k),k=1..n)),n=1..10); # Peter Luschny, Feb 02 2015
# Alternative:
A079618row := proc(n) bernoulli(n,x); (subs(x=x+1,%)-subs(x=1,%))/n;
seq(coeff(numer(%),x,k), k=1..n) end:
seq(A079618row(n), n=1..13); # Peter Luschny, Jul 14 2020

T[n_, k_] := T[n, k] = Module[{A, B}, A[m_] := A[m] = Denominator[ Together[ (BernoulliB[m+1, x] - BernoulliB[m+1])/(m+1)]]; B[m_] := B[m] = Sum[T[m, j], {j, 2, m}]; Which[k>1, T[n-1, k-1]*(n-1)*A[n-1]/(k*A[n-2]), n>1, A[n-1] - B[n], True, 1]]; Table[Table[T[n, k], {k, 1, n}], {n, 1, 10}] // Flatten (* Jean-François Alcover, Sep 04 2015, after Peter Luschny *)

row(p) = {v = vector(p+1, k, (-1)^(k==p)*binomial(p+1, k)*bernfrac(p+1-k))/(p+1); lcmd = lcm(vector(#v, k, denominator(v[k]))); v*lcmd;}
tabl(nn) = for (n=0, nn, print(row(n))); \\ Michel Marcus, Feb 16 2016

T(n, k) = T(n-1, k-1) * (n-1) * A064538(n-1) / (k*A064538(n-2)) for k>1; T(n, 1) = A064538(n-1) - Sum_{k=2..n} T(n, k) for n>1; T(1, 1)=1.

Edited. Offset corrected from 0 to 1. Typo in formula corrected. - Wolfdieter Lang, Feb 02 2015

A342322 T(n, k) = A064538(n)[x^k] p(n, x) where p(n, x) = 1 + Sum_{k = 0..n-1} binomial[n, k]p(k, 1)* ((x - 1)^(n - k) - 1) / (n - k + 1) for n >= 1 and p(0, x) = 1. Triangle read by rows, for 0 <= k <= n.

Original entry on oeis.org

1, 0, 1, 0, -1, 2, 0, 0, -1, 1, 0, 1, 1, -9, 6, 0, 0, 1, 1, -4, 2, 0, -1, -1, 6, 6, -15, 6, 0, 0, -2, -2, 5, 5, -9, 3, 0, 3, 3, -17, -17, 25, 25, -35, 10, 0, 0, 3, 3, -7, -7, 7, 7, -8, 2, 0, -5, -5, 28, 28, -38, -38, 28, 28, -27, 6, 0, 0, -10, -10, 23, 23, -21, -21, 12, 12, -10, 2

Offset: 0

Peter Luschny, Mar 09 2021

			p(n, x) = (Sum_{k = 0..n} T(n, k) x^k) / A064538(n).
[n]                T(n, k)               A064538(n)
---------------------------------------------------
[0] 1,                                         [ 1]
[1] 0,  1,                                     [ 2]
[2] 0, -1,  2,                                 [ 6]
[3] 0,  0, -1,   1,                            [ 4]
[4] 0,  1,  1,  -9,   6,                       [30]
[5] 0,  0,  1,   1,  -4,   2,                  [12]
[6] 0, -1, -1,   6,   6, -15,  6,              [42]
[7] 0,  0, -2,  -2,   5,   5, -9,   3,         [24]
[8] 0,  3,  3, -17, -17,  25, 25, -35, 10,     [90]
[9] 0,  0,  3,   3,  -7,  -7,  7,   7, -8, 2.  [20]

Cf. A064538.

CoeffList := p -> [op(PolynomialTools:-CoefficientList(factor(p), x))]:
p := n -> add(binomial(n+1,k+1)*bernoulli(n-k, 1)*(x-1)^k, k=0..n)/(n+1):
seq(print(denom(p(n))*CoeffList(p(n))), n=0..9);

(* Uses the function A064538. *)
p[n_, x_] := p[n, x] = If[n == 0, 1, 1 +
Sum[Binomial[n, k] p[k, 1] ((x - 1)^(n - k) - 1) / (n - k + 1), {k, 0, n-1}]];
Table[A064538[n] CoefficientList[p[n, x], x][[k+1]], {n, 0, 9}, {k, 0, n}] // Flatten

(Sum_{k = 0..n} T(n, k)) / A064538(n) = Bernoulli(n, 1).

A000538 Sum of fourth powers: 0^4 + 1^4 + ... + n^4.

Original entry on oeis.org

0, 1, 17, 98, 354, 979, 2275, 4676, 8772, 15333, 25333, 39974, 60710, 89271, 127687, 178312, 243848, 327369, 432345, 562666, 722666, 917147, 1151403, 1431244, 1763020, 2153645, 2610621, 3142062, 3756718, 4463999, 5273999, 6197520, 7246096, 8432017, 9768353

Offset: 0

N. J. A. Sloane

This sequence is related to A000537 by the transform a(n) = n*A000537(n) - Sum_{i=0..n-1} A000537(i). - Bruno Berselli, Apr 26 2010
A formula for the r-th successive summation of k^4, for k = 1 to n, is ((12*n^2+(12*n-5)*r+r^2)*(2*n+r)*(n+r)!)/((r+4)!*(n-1)!), (H. W. Gould). - Gary Detlefs, Jan 02 2014
The number of four dimensional hypercubes in a 4D grid with side lengths n. This applies in general to k dimensions. That is, the number of k-dimensional hypercubes in a k-dimensional grid with side lengths n is equal to the sum of 1^k + 2^k + ... + n^k. - Alejandro Rodriguez, Oct 20 2020

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 813.
A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, id. 222.
L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 155.
R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1991, p. 275.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

T. D. Noe, Table of n, a(n) for n = 0..1000
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
J. L. Bailey, Jr., A table to facilitate the fitting of certain logistic curves, Annals Math. Stat., 2 (1931), 355-359.
J. L. Bailey, A table to facilitate the fitting of certain logistic curves, Annals Math. Stat., 2 (1931), 355-359. [Annotated scanned copy]
Bruno Berselli, A description of the transform in Comments lines: website Matem@ticamente (in Italian).
Stefano Capparelli, Notes on Discrete Math, Società Editrice Esculapio SRL (2019) 3-4.
Feihu Liu, Guoce Xin, and Chen Zhang, Ehrhart Polynomials of Order Polytopes: Interpreting Combinatorial Sequences on the OEIS, arXiv:2412.18744 [math.CO], 2024. See p. 13.
Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992
Eric Weisstein, MathWorld: Faulhaber's Formula
Wikipedia, Faulhaber's formula
Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

Cf. A000217, A000330, A000537, A000539, A000540, A000541, A000542, A007487, A023002, A064538, A101089.
Row 4 of array A103438.
Cf. A000583.
Cf. A254640.

a000538 n = (3 * n * (n + 1) - 1) * (2 * n + 1) * (n + 1) * n `div` 30
-- Reinhard Zumkeller, Nov 11 2012

[n*(1+n)*(1+2*n)*(-1+3*n+3*n^2)/30: n in [0..35]]; // Vincenzo Librandi, Apr 04 2015

A000538 := n-> n*(n+1)*(2*n+1)*(3*n^2+3*n-1)/30;

Accumulate[Range[0,40]^4] (* Harvey P. Dale, Jan 13 2011 *)
CoefficientList[Series[x (1 + 11 x + 11 x^2 + x^3)/(1 - x)^6, {x, 0, 40}], x] (* Vincenzo Librandi, Dec 07 2015 *)
LinearRecurrence[{6, -15, 20, -15, 6, -1}, {0, 1, 17, 98, 354, 979}, 35] (* Jean-François Alcover, Feb 09 2016 *)
Table[x^5/5+x^4/2+x^3/3-x/30,{x,40}] (* Harvey P. Dale, Jun 06 2021 *)

A000538(n):=n*(n+1)*(2*n+1)*(3*n^2+3*n-1)/30$
makelist(A000538(n),n,0,30); /* Martin Ettl, Nov 12 2012 */

a(n) = n*(1+n)*(1+2*n)*(-1+3*n+3*n^2)/30 \\ Charles R Greathouse IV, Nov 20 2012

concat(0, Vec(x*(1+11*x+11*x^2+x^3)/(1-x)^6 + O(x^100))) \\ Altug Alkan, Dec 07 2015

A000538_list, m = [0], [24, -36, 14, -1, 0, 0]
for _ in range(10**2):
    for i in range(5):
        m[i+1] += m[i]
    A000538_list.append(m[-1]) # Chai Wah Wu, Nov 05 2014

def A000538(n): return n*(n**2*(n*(6*n+15)+10)-1)//30 # Chai Wah Wu, Oct 03 2024

[bernoulli_polynomial(n,5)/5 for n in range(1, 35)] # Zerinvary Lajos, May 17 2009

a(n) = n*(1+n)*(1+2*n)*(-1+3*n+3*n^2)/30.
The preceding formula is due to al-Kachi (1394-1437). - Juri-Stepan Gerasimov, Jul 12 2009
G.f.: x*(x+1)*(1+10*x+x^2)/(1-x)^6. Simon Plouffe in his 1992 dissertation. More generally, the o.g.f. for Sum_{k=0..n} k^m is x*E(m, x)/(1-x)^(m+2), where E(m, x) is the Eulerian polynomial of degree m (cf. A008292). The e.g.f. for these o.g.f.s is: x/(1-x)^2*(exp(y/(1-x))-exp(x*y/(1-x)))/(exp(x*y/(1-x))-x*exp(y/(1-x))). - Vladeta Jovovic, May 08 2002
a(n) = Sum_{i = 1..n} J_4(i)*floor(n/i), where J_4 is A059377. - Enrique Pérez Herrero, Feb 26 2012
a(n) = 5*a(n-1) - 10* a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) + 24. - Ant King, Sep 23 2013
a(n) = -Sum_{j=1..4} j*Stirling1(n+1,n+1-j)*Stirling2(n+4-j,n). - Mircea Merca, Jan 25 2014
Sum_{n>=1} (-1)^(n+1)/a(n) = -30*(4 + 3/cos(sqrt(7/3)*Pi/2))*Pi/7. - Vaclav Kotesovec, Feb 13 2015
a(n) = (n + 1)*(n + 1/2)*n*(n + 1/2 + sqrt(7/12))*(n + 1/2  - sqrt(7/12))/5, see the Graham et al. reference, p. 275. - Wolfdieter Lang, Apr 02 2015

The general V. Jovovic formula has been slightly changed after his approval by Wolfdieter Lang, Nov 03 2011

A144845 Least number k such that all coefficients of k*B(n,x), the n-th Bernoulli polynomial, are integers.

Original entry on oeis.org

1, 2, 6, 2, 30, 6, 42, 6, 30, 10, 66, 6, 2730, 210, 30, 6, 510, 30, 3990, 210, 2310, 330, 690, 30, 2730, 546, 42, 14, 870, 30, 14322, 462, 39270, 3570, 210, 6, 1919190, 51870, 2730, 210, 94710, 2310, 99330, 2310, 4830, 4830, 9870, 210, 46410, 6630, 14586, 858

Offset: 0

T. D. Noe, Sep 22 2008

nonn

The lcm of the terms in row n of A053383. It appears that the Bernoulli polynomial B(n,x) is irreducible for all even n.
This sequence appears in a paper of Bazsó & Mező, who use this sequence to give necessary and sufficient conditions for power sums to be integer polynomials. - Istvan Mezo, Mar 20 2016
In "The denominators of power sums of arithmetic progressions" Corollary 1, we give a simple way to compute a(n) without using Bernoulli polynomials. Namely, a(n) equals (product of the primes dividing n+1) times (product of the primes p <= (n+1)/(2+(n+1 mod 2)) not dividing n+1 such that the sum of the base-p digits of n+1 is at least p). - Bernd C. Kellner and Jonathan Sondow, May 15 2017

Bernd C. Kellner, Table of n, a(n) for n = 0..10000 (n = 0..1000 from T. D. Noe)
András Bazsó and István Mező, On the coefficients of power sums of arithmetic progressions, J. Number Th., 153 (2015), 117-123.
András Bazsó and István Mező, Some Notes on Alternating Power Sums of Arithmetic Progressions, J. Int. Seq., Vol. 21 (2018), Article 18.7.8.
Bernd C. Kellner, On a product of certain primes, J. Number Theory, 179 (2017), 126-141; arXiv:1705.04303 [math.NT], 2017.
Bernd C. Kellner, On the finiteness of Bernoulli polynomials whose derivative has only integral coefficients, J. Integer Seq. 27 (2024), Article 24.2.8, 11 pp.; arXiv:2310.01325 [math.NT], 2023.
Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, The denominators of power sums of arithmetic progressions, Integers 18 (2018), #A95, 17 pp.; arXiv:1705.05331 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, On Carmichael and polygonal numbers, Bernoulli polynomials, and sums of base-p digits, Integers 21 (2021), #A52, 21 pp.; arXiv:1902.10672 [math.NT], 2019.
Eric Weisstein's World of Mathematics, Bernoulli Polynomial.

Cf. A027642, A053383, A064538, A195441, A286515, A286516, A286517, A324369, A324370, A324371.

seq(denom(bernoulli(i,x)),i=0..51); # Peter Luschny, Jun 16 2012

(* From Bernd C. Kellner, Oct 18 2023: (Start) *)
(* Denominator formula *)
Table[Denominator[Together[BernoulliB[n, x]]], {n, 0, 51}]
(* Product formula *)
SD[n_, p_] := If[n < 1 || p < 2, 0, Plus@@IntegerDigits[n, p]]; rad[n_] := Times @@ Select[Divisors[n], PrimeQ]; (* A324370 *) DD2[n_] := Times @@ Select[Prime[Range[PrimePi[(n+1)/(2+Mod[n+1, 2])]]], !Divisible[n, #] && SD[n, #] >= # &];
DB[n_] := DD2[n+1] rad[n+1]; Table[DB[n], {n, 0, 51}]
(* (End) *)

a(n) = lcm(apply(x->denominator(x), Vec(bernpol(n)))); \\ Michel Marcus, Mar 03 2020

def A144845(n):
    return mul(prime_divisors(n+1) + [p for p in (2..(n+2)//(2+n%2))
    if is_prime(p) and not p.divides(n+1) and sum((n+1).digits(base=p)) >= p])
print([A144845(n) for n in (0..51)]) # Peter Luschny, Sep 12 2018

From Bernd C. Kellner, Oct 18 2023: (Start)
Let rad(n) = A007947(n) be the radical of n. Let (n)_m be the falling factorial. Let f^(m)(x) denote the m-th derivative of f(x).
a(n) = lcm(A195441(n-1), A027642(n)) = lcm(denom(B(n,x)-B_n), denom(B_n)) = denom(B(n,x)).
a(n) = lcm(A195441(n), rad(n+1)).
a(n) = lcm(a(n+1), rad(n+1)), if n >= 2 is even.
a(2n)/a(2n+1) = A286517(n), if n >= 1.
a(n) = A324369(n+1) * A324370(n+1) * A324371(n+1).
a(n) = A324370(n+1) * rad(n+1).
a(n) = rad(A064538(n)).
If n >= m >= 1, then denom(B^(m)(n,x)) = a(n-m)/gcd(a(n-m), (n)A324370(n-m+1)/gcd(A324370(n-m+1),%20(n)">m) = A324370(n-m+1)/gcd(A324370(n-m+1), (n){m-1}).
(See papers of Kellner and Kellner & Sondow.) (End)

A195441 a(n) = denominator(Bernoulli_{n+1}(x) - Bernoulli_{n+1}).

Original entry on oeis.org

1, 1, 2, 1, 6, 2, 6, 3, 10, 2, 6, 2, 210, 30, 6, 3, 30, 10, 210, 42, 330, 30, 30, 30, 546, 42, 14, 2, 30, 2, 462, 231, 3570, 210, 6, 2, 51870, 2730, 210, 42, 2310, 330, 2310, 210, 4830, 210, 210, 210, 6630, 1326, 858, 66, 330, 110, 798, 114, 870, 30, 30, 6

Offset: 0

Peter Luschny, Sep 18 2011

nonn

If s(n) is the smallest number such that s(n)*(1^n + 2^n + ... + x^n) is a polynomial in x with integer coefficients then a(n)=s(n)/(n+1) (see A064538).
a(n) is squarefree, by the von Staudt-Clausen theorem on the denominators of Bernoulli numbers. - Kieren MacMillan and Jonathan Sondow, Nov 20 2015
Kellner and Sondow give a detailed analysis of this sequence and provide a simple way to compute the terms without using Bernoulli polynomials and numbers. They prove that a(n) is the product of the primes less than or equal to (n+2)/(2+(n mod 2)) such that the sum of digits of n+1 in base p is at least p. - Peter Luschny, May 14 2017
The equation a(n-1) = denominator(Bernoulli_n(x) - Bernoulli_n) = rad(n+1) has only finitely many solutions, where rad(n) = A007947(n) is the radical of n. It is conjectured that S = {3, 5, 8, 9, 11, 27, 29, 35, 59} is the full set of all such solutions. Note that (S\{8})+1 joined with {1,2} equals A094960. More precisely, the set S implies the finite sequence of A094960. See Kellner 2023. - Bernd C. Kellner, Oct 18 2023
As was observed in the example section of A318256: denominator(B_n(x)) = rad(n+1) if n is in {0, 1, 3, 5, 9, 11, 27, 29, 35, 59} = {A094960(n) - 1: 1 <= n <= 10}. - Peter Luschny, Oct 18 2023

Peter Luschny, Table of n, a(n) for n = 0..10000 (terms 0..1000 from G. C. Greubel)
Olivier Bordellès, Florian Luca, Pieter Moree, and Igor E. Shparlinski, Denominators of Bernoulli polynomials, Mathematika 64 (2018), 519-541.
Harald Hofstätter, Denominators of coefficients of the Baker-Campbell-Hausdorff series, arXiv:2010.03440 [math.NT], 2020. Mentions this sequence.
Bernd C. Kellner, On a product of certain primes, J. Number Theory, 179 (2017), 126-141; arXiv:1705.04303 [math.NT], 2017.
Bernd C. Kellner, On the finiteness of Bernoulli polynomials whose derivative has only integral coefficients, J. Integer Seq. 27 (2024), Article 24.2.8, 11 pp.; arXiv:2310.01325 [math.NT], 2023.
Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, The denominators of power sums of arithmetic progressions, Integers 18 (2018), #A95, 17 pp.; arXiv:1705.05331 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, On Carmichael and polygonal numbers, Bernoulli polynomials, and sums of base-p digits, Integers 21 (2021), #A52, 21 pp.; arXiv:1902.10672 [math.NT], 2019.

Cf. A002997, A064538, A094960, A144845, A286516, A286762, A286763, A318256, A324369, A324370, A324371.

using Nemo, Primes
function A195441(n::Int)
    n < 4 && return ZZ([1,1,2,1][n+1])
    P = primes(2, div(n+2, 2+n%2))
    prod([ZZ(p) for p in P if p <= sum(digits(n+1, base=p))])
end
println([A195441(n) for n in 0:59]) # Peter Luschny, May 14 2017

A195441 := n -> denom(bernoulli(n+1, x)-bernoulli(n+1)):
seq(A195441(i),i=0..59);
# Formula of Kellner and Sondow:
a := proc(n) local s; s := (p,n) -> add(i,i=convert(n,base,p));
select(isprime,[$2..(n+2)/(2+irem(n,2))]); mul(i,i=select(p->s(p,n+1)>=p,%)) end: seq(a(n), n=0..59); # Peter Luschny, May 14 2017

a[n_] := Denominator[Together[(BernoulliB[n + 1, x] - BernoulliB[n + 1])]]; Table[a[n], {n, 0, 59}] (* Jonathan Sondow, Nov 20 2015 *)
SD[n_, p_] := If[n < 1 || p < 2, 0, Plus @@ IntegerDigits[n, p]]; DD[n_] := Times @@ Select[Prime[Range[PrimePi[(n+2)/(2+Mod[n, 2])]]], SD[n+1, #] >= # &]; Table[DD[n], {n, 0, 59}] (* Bernd C. Kellner, Oct 18 2023 *)

a(n) = {my(vp = Vec(bernpol(n+1, x)-bernfrac(n+1))); lcm(vector(#vp, k, denominator(vp[k])));} \\ Michel Marcus, Feb 08 2016

from math import prod
from sympy.ntheory.factor_ import primerange, digits
def A195441(n): return prod(p for p in primerange((n+2)//(2|n&1)+1) if sum(digits(n+1,p)[1:])>=p) # Chai Wah Wu, Oct 04 2023

A195441 = lambda n: mul([p for p in (2..(n+2)//(2+n%2)) if is_prime(p) and sum((n+1).digits(base=p))>=p])
print([A195441(n) for n in (0..59)]) # Peter Luschny, May 14 2017

a(n) = A064538(n)/(n+1). - Jonathan Sondow, Nov 12 2015
A001221(a(n)) = A001222(a(n)). - Kieren MacMillan and Jonathan Sondow, Nov 20 2015
a(2*n)/a(2*n+1) = A286516(n+1). - Bernd C. Kellner and Jonathan Sondow, May 24 2017
a(n) = A007947(A338025(n+1)). - Harald Hofstätter, Oct 10 2020
From Bernd C. Kellner, Oct 18 2023: (Start)
Note that the formulas here are shifted in index by 1 due to the definition of a(n) using index n+1!
a(n) = A324369(n+1) * A324370(n+1).
a(n) = A144845(n) / A324371(n+1).
a(n-1) = lcm(a(n), rad(n+1)), if n >= 3 is odd.
If n+1 is composite, then rad(n+1) divides a(n-1).
If m is a Carmichael number (A002997), then m divides both a(m-1) and a(m-2).
See papers of Kellner and Kellner & Sondow. (End)

Definition simplified by Jonathan Sondow, Nov 20 2015

A286516 a(n) = b(2n-1)/b(2n) where b(n) = A195441(n-1) = denominator(Bernoulli_{n}(x) - Bernoulli_{n}).

Original entry on oeis.org

1, 2, 3, 2, 5, 3, 7, 2, 3, 5, 11, 1, 13, 7, 15, 2, 17, 3, 19, 5, 7, 11, 23, 1, 5, 13, 3, 7, 29, 5, 31, 2, 11, 17, 7, 1, 37, 19, 13, 5, 41, 21, 43, 11, 3, 23, 47, 1, 7, 5, 17, 13, 53, 3, 11, 7, 19, 29, 59, 1, 61, 31, 7, 2, 65, 11, 67, 17, 23, 5, 71, 1, 73, 37

Offset: 1

Bernd C. Kellner and Jonathan Sondow, May 12 2017

nonn

a(n) is an integer for all n, a(n) is odd if n is not a power of 2, a(2^k)=2 for all k>=1, a(n)=1 infinitely often, and a(n)=p infinitely often for every prime p. See Cor. 2 and Cor. 3 in "The denominators of power sums of arithmetic progressions". See also "Power-sum denominators".

G. C. Greubel, Table of n, a(n) for n = 1..1000
Bernd C. Kellner, On a product of certain primes, J. Number Theory, 179 (2017), 126-141; arXiv:1705.04303 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, The denominators of power sums of arithmetic progressions, Integers 18 (2018), #A95, 17 pp.; arXiv:1705.05331 [math.NT], 2017.

Cf. A027642, A064538, A144845, A195441, A286515, A286517, A286762, A286763.

b[n_] := Denominator[ Together[ BernoulliB[n, x] - BernoulliB[n]]]; Table[
b[2 n - 1]/b[2 n], {n, 1, 74}]

a(n) = A195441(2*n-2) / A195441(2*n-1).

A256581 Number of conditions on m under which m^n + (m+1)^n + ... + (m+k)^n is composite for every k>=1 (see comment).

Original entry on oeis.org

2, 3, 2, 7, 5, 7, 7, 11, 5, 7, 7, 31, 23, 11, 9, 15, 17, 31, 31, 47, 23, 15, 29, 47, 23, 15, 7, 15, 11, 31, 47, 95, 47, 15, 11, 127, 95, 47, 39, 63, 71, 63, 63, 95, 47, 31, 71, 95, 71, 47, 31, 31, 47, 63, 39, 47, 23, 15, 23, 255, 191, 127, 111, 95, 71, 127

Offset: 1

Vladimir Shevelev, Apr 02 2015

nonn

We consider a(n), n>=2, conditions of the form: all numbers P_i(m) are composite, i = 1, ..., a(n), where P_i(m) is a polynomial of power n+1. It could be proved that S_k(m)= m^n + (m+1)^n + ... + (m+k)^n, as a polynomial in m of degree n+1, is divisible by k+1. Let S*_k(m) = S_k(m)/(k+1). So we have
S_k(m)=S*_k(m)*(k+1)=(T_k(m)/b(n))*(k+1), (1)
where b(n)=A064538(n) and, by the definition of A064538, T_k(m) = b(n)*S*_k(m) is a polynomial with integer coefficients.
It is clear that (1) could be prime only if k+1>=2 is a divisor of b(n). In this case we should require that (1) be a composite number. We have exactly A000005(b(n))-1 such requirements. In case of n=1, a(n)=2 (see A089306, A077654).
Remark. Sometimes some considered conditions satisfy trivially. For example, both a(3)=2 conditions for every  m>=2 evidently hold, such that every number of the form m^3 + (m+1)^3 + ... +(m+k)^3 is composite.
Note that essentially this method is useful only in case of even n. Indeed, according to our comment in A001017, in case of odd n>=3 the number m^n + (m+1)^n + ... + (m+k)^n is composite for every k>=1. - Vladimir Shevelev, Apr 06 2015

Peter J. C. Moses, Table of n, a(n) for n = 1..1000

Cf. A000005, A064538, A089306 (a(1)=2), A256385 (a(2)=3), A256546 (a(4)=7).

For n>=2, a(n) = A000005(A064538(n))-1.

More terms from Peter J. C. Moses, Apr 02 2015

A318256 a(n) = (denominator of B(n,x)) / (the squarefree kernel of n+1), where B(n,x) is the n-th Bernoulli polynomial.

Original entry on oeis.org

1, 1, 2, 1, 6, 1, 6, 3, 10, 1, 6, 1, 210, 15, 2, 3, 30, 5, 210, 21, 110, 15, 30, 5, 546, 21, 14, 1, 30, 1, 462, 231, 1190, 105, 6, 1, 51870, 1365, 70, 21, 2310, 55, 2310, 105, 322, 105, 210, 35, 6630, 663, 286, 33, 330, 55, 798, 57, 290, 15, 30, 1, 930930, 15015

Offset: 0

Peter Luschny, Sep 12 2018

nonn

			a(59) = 1 because there exist no number which satisfies the definition (and the product of an empty set is 1).
a(60) = 930930 because {2, 3, 5, 7, 11, 13, 31} are the only primes which satisfy the definition.
The denominator of the Bernoulli polynomial B_n(x) equals the squarefree kernel of n+1 if n is in {0, 1, 3, 5, 9, 11, 27, 29, 35, 59}. These might be the only numbers with this property.

Peter Luschny, Table of n, a(n) for n = 0..1000
András Bazsó and István Mező, On the coefficients of power sums of arithmetic progressions, J. Number Th., 153 (2015), 117-123.
Bernd C. Kellner, On a product of certain primes, J. Number Theory, 179 (2017), 126-141; arXiv:1705.04303 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, The denominators of power sums of arithmetic progressions, Integers 18 (2018), #A95, 17 pp.; arXiv:1705.05331 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, On Carmichael and polygonal numbers, Bernoulli polynomials, and sums of base-p digits, Integers 21 (2021), #A52, 21 pp.; arXiv:1902.10672 [math.NT], 2019.
Bernd C. Kellner, On the finiteness of Bernoulli polynomials whose derivative has only integral coefficients, 9 pp.; arXiv:2310.01325 [math.NT], 2023.

a(n) = A144845(n) / A007947(n+1).
Cf. A324370 (same sequence with offset 1).
Cf. A027642, A064538, A195441, A286515, A286516, A286517, A286762, A286763, A319084.

a := n -> denom(bernoulli(n, x)) / mul(p, p in numtheory:-factorset(n+1)):
seq(a(n), n=0..61);

sfk[n_] := Times @@ FactorInteger[n][[All, 1]];
a[n_] := (BernoulliB[n, x] // Together // Denominator)/sfk[n+1];
Table[a[n], {n, 0, 61}] (* Jean-François Alcover, Feb 14 2019 *)

def A318256(n): return mul([p for p in (2..(n+2)//(2+n%2))
                if is_prime(p)
                and not p.divides(n+1)
                and sum((n+1).digits(base=p)) >= p])
print([A318256(n) for n in (0..61)])

Let Q(n) = {p <= floor((n + 2)/(2 + n mod 2)) and p is prime and p does not divide n + 1 and the sum of the digits in base p of n+1 is at least p} then a(n) = Product_{p in Q(n)} p. (See the Kellner & Sondow links.)

a(n) = denominator(Bernoulli'(n+1, x)), where ' denotes d/dx. - Peter Luschny, Oct 15 2023

A286515 a(n) = denominator(Bernoulli_{n}(x)) / denominator(Bernoulli_{n}).

Original entry on oeis.org

1, 1, 1, 2, 1, 6, 1, 6, 1, 10, 1, 6, 1, 210, 5, 6, 1, 30, 5, 210, 7, 330, 5, 30, 1, 546, 7, 14, 1, 30, 1, 462, 77, 3570, 35, 6, 1, 51870, 455, 210, 7, 2310, 55, 2310, 7, 4830, 35, 210, 1, 6630, 221, 858, 11, 330, 55, 798, 19, 870, 5, 30, 1, 930930, 5005, 4290

Offset: 0

Bernd C. Kellner and Jonathan Sondow, May 11 2017

nonn

a(n) is a squarefree integer for all n, a(n) is odd if n>=0 is even, and a(n) is even if n>=3 is odd. See "Power-sum denominators", Thm. 4, pp. 12-13, and "The denominators of power sums of arithmetic progressions", Thm. 3, pp. 3 and 11-12.

Robert Israel, Table of n, a(n) for n = 0..5900
Bernd C. Kellner, On a product of certain primes, J. Number Theory, 179 (2017), 126-141; arXiv:1705.04303 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, The denominators of power sums of arithmetic progressions, Integers 18 (2018), #A95, 17 pp.; arXiv:1705.05331 [math.NT], 2017.

Cf. A027642, A064538, A144845, A195441, A286516, A286517.

seq(denom(bernoulli(n,x))/denom(bernoulli(n)), n=0..100); # Robert Israel, May 24 2017

Table[ Denominator[ Together[ BernoulliB[n, x]]]/Denominator[ BernoulliB[n]], {n, 0, 63}]

apply( a(n)=denominator(content(bernpol(n)))/denominator(bernfrac(n)), [1..50]) \\ M. F. Hasler, Dec 10 2018

a(n) = A144845(n)/A027642(n) = A195441(n-1)/gcd(A195441(n-1),A027642(n)).

A286517 a(n) = b(2n)/b(2n+1) where b(n) = denominator(Bernoulli_{n}(x)).

Original entry on oeis.org

3, 5, 7, 3, 11, 13, 5, 17, 19, 7, 23, 5, 3, 29, 31, 11, 35, 37, 13, 41, 43, 1, 47, 7, 17, 53, 55, 19, 59, 61, 7, 13, 67, 23, 71, 73, 5, 77, 79, 3, 83, 17, 29, 89, 13, 31, 19, 97, 11, 101, 103, 7, 107, 109, 37, 113, 23, 13, 119, 11, 41, 5, 127, 43, 131, 19, 5

Offset: 1

Bernd C. Kellner and Jonathan Sondow, May 12 2017

nonn

a(n) is an odd integer for all n, a(n)=1 infinitely often, and a(n)=p infinitely often for every odd prime p. See Cor. 2 and Cor. 3 in "The denominators of power sums of arithmetic progressions". See also "Power-sum denominators".

G. C. Greubel, Table of n, a(n) for n = 1..1000
Bernd C. Kellner, On a product of certain primes, J. Number Theory, 179 (2017), 126-141; arXiv:1705.04303 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017.
Bernd C. Kellner and Jonathan Sondow, The denominators of power sums of arithmetic progressions, Integers 18 (2018), #A95, 17 pp.; arXiv:1705.05331 [math.NT], 2017.

Cf. A027642, A064538, A144845, A195441, A286515, A286516.

b[n_] := Denominator[ Together[ BernoulliB[n, x]]]; Table[ b[2 n]/b[2 n + 1], {n, 1, 67}]

a(n) = A144845(2*n) / A144845(2*n+1) for n >= 1.

cp's OEIS Frontend

A079618 Triangle of coefficients in polynomials for partial sums of powers, scaled to produce integers: Sum_{i=1..m} i^(n-1) = Sum_{k=1..n} T(n,k)*m^k/A064538(n-1).

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A342322 T(n, k) = A064538(n)*[x^k] p(n, x) where p(n, x) = 1 + Sum_{k = 0..n-1} binomial[n, k]*p(k, 1)* ((x - 1)^(n - k) - 1) / (n - k + 1) for n >= 1 and p(0, x) = 1. Triangle read by rows, for 0 <= k <= n.

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A000538 Sum of fourth powers: 0^4 + 1^4 + ... + n^4.

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A144845 Least number k such that all coefficients of k*B(n,x), the n-th Bernoulli polynomial, are integers.

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A195441 a(n) = denominator(Bernoulli_{n+1}(x) - Bernoulli_{n+1}).

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A286516 a(n) = b(2*n-1)/b(2*n) where b(n) = A195441(n-1) = denominator(Bernoulli_{n}(x) - Bernoulli_{n}).

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A342322 T(n, k) = A064538(n)[x^k] p(n, x) where p(n, x) = 1 + Sum_{k = 0..n-1} binomial[n, k]p(k, 1)* ((x - 1)^(n - k) - 1) / (n - k + 1) for n >= 1 and p(0, x) = 1. Triangle read by rows, for 0 <= k <= n.

A286516 a(n) = b(2n-1)/b(2n) where b(n) = A195441(n-1) = denominator(Bernoulli_{n}(x) - Bernoulli_{n}).

A286517 a(n) = b(2n)/b(2n+1) where b(n) = denominator(Bernoulli_{n}(x)).