cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-9 of 9 results.

A000169 Number of labeled rooted trees with n nodes: n^(n-1).

Original entry on oeis.org

1, 2, 9, 64, 625, 7776, 117649, 2097152, 43046721, 1000000000, 25937424601, 743008370688, 23298085122481, 793714773254144, 29192926025390625, 1152921504606846976, 48661191875666868481, 2185911559738696531968, 104127350297911241532841, 5242880000000000000000000
Offset: 1

Views

Author

N. J. A. Sloane

Keywords

Comments

Also the number of connected transitive subtree acyclic digraphs on n vertices. - Robert Castelo, Jan 06 2001
For any given integer k, a(n) is also the number of functions from {1,2,...,n} to {1,2,...,n} such that the sum of the function values is k mod n. - Sharon Sela (sharonsela(AT)hotmail.com), Feb 16 2002
The n-th term of a geometric progression with first term 1 and common ratio n: a(1) = 1 -> 1,1,1,1,... a(2) = 2 -> 1,2,... a(3) = 9 -> 1,3,9,... a(4) = 64 -> 1,4,16,64,... - Amarnath Murthy, Mar 25 2004
All rational solutions to the equation x^y = y^x, with x < y, are given by x = A000169(n+1)/A000312(n), y = A000312(n+1)/A007778(n), where n = 1, 2, 3, ... . - Nick Hobson, Nov 30 2006
a(n+1) is also the number of partial functions on n labeled objects. - Franklin T. Adams-Watters, Dec 25 2006
In other words, if A is a finite set of size n-1, then a(n) is the number of binary relations on A that are also functions. Note that a(n) = Sum_{k=0..n-1} binomial(n-1,k)*(n-1)^k = n^(n-1), where binomial(n-1,k) is the number of ways to select a domain D of size k from A and (n-1)^k is the number of functions from D to A. - Dennis P. Walsh, Apr 21 2011
This is the fourth member of a set of which the other members are the symmetric group, full transformation semigroup, and symmetric inverse semigroup. For the first three, see A000142, A000312, A002720. - Peter J. Cameron, Nov 03 2024.
More generally, consider the class of sequences of the form a(n) = (n*c(1)*...*c(i))^(n-1). This sequence has c(1)=1. A052746 has a(n) = (2*n)^(n-1), A052756 has a(n) = (3*n)^(n-1), A052764 has a(n) = (4*n)^(n-1), A052789 has a(n) = (5*n)^(n-1) for n>0. These sequences have a combinatorial structure like simple grammars. - Ctibor O. Zizka, Feb 23 2008
a(n) is equal to the logarithmic transform of the sequence b(n) = n^(n-2) starting at b(2). - Kevin Hu (10thsymphony(AT)gmail.com), Aug 23 2010
Also, number of labeled connected multigraphs of order n without cycles except one loop. See link below to have a picture showing the bijection between rooted trees and multigraphs of this kind. (Note that there are no labels in the picture, but the bijection remains true if we label the nodes.) - Washington Bomfim, Sep 04 2010
a(n) is also the number of functions f:{1,2,...,n} -> {1,2,...,n} such that f(1) = 1.
For a signed version of A000169 arising from the Vandermonde determinant of (1,1/2,...,1/n), see the Mathematica section. - Clark Kimberling, Jan 02 2012
Numerator of (1+1/(n-1))^(n-1) for n>1. - Jean-François Alcover, Jan 14 2013
Right edge of triangle A075513. - Michel Marcus, May 17 2013
a(n+1) is the number of n x n binary matrices with no more than a single one in each row. Partitioning the set of such matrices by the number k of rows with a one, we obtain a(n+1) = Sum_{k=0..n} binomial(n,k)*n^k = (n+1)^n. - Dennis P. Walsh, May 27 2014
Central terms of triangle A051129: a(n) = A051129(2*n-1,n). - Reinhard Zumkeller, Sep 14 2014
a(n) is the row sum of the n-th rows of A248120 and A055302, so it enumerates the monomials in the expansion of [x(1) + x(2) + ... + x(n)]^(n-1). - Tom Copeland, Jul 17 2015
For any given integer k, a(n) is the number of sums x_1 + ... + x_m = k (mod n) such that: x_1, ..., x_m are nonnegative integers less than n, the order of the summands does not matter, and each integer appears fewer than n times as a summand. - Carlo Sanna, Oct 04 2015
a(n) is the number of words of length n-1 over an alphabet of n letters. - Joerg Arndt, Oct 07 2015
a(n) is the number of parking functions whose largest element is n and length is n. For example, a(3) = 9 because there are nine such parking functions, namely (1,2,3), (1,3,2), (2,3,1), (2,1,3), (3,1,2), (3,2,1), (1,1,3), (1,3,1), (3,1,1). - Ran Pan, Nov 15 2015
Consider the following problem: n^2 cells are arranged in a square array. A step can be defined as going from one cell to the one directly above it, to the right of it or under it. A step above cannot be followed by a step below and vice versa. Once the last column of the square array is reached, you can only take steps down. a(n) is the number of possible paths (i.e., sequences of steps) from the cell on the bottom left to the cell on the bottom right. - Nicolas Nagel, Oct 13 2016
The rationals c(n) = a(n+1)/a(n), n >= 1, appear in the proof of G. Pólya's "elementary, but not too elementary, theorem": Sum_{n>=1} (Product_{k=1..n} a_k)^(1/n) < exp(1)*Sum_{n>=1} a_n, for n >= 1, with the sequence {a_k}{k>=1} of nonnegative terms, not all equal to 0. - _Wolfdieter Lang, Mar 16 2018
Coefficients of the generating series for the preLie operadic algebra. Cf. p. 417 of the Loday et al. paper. - Tom Copeland, Jul 08 2018
a(n)/2^(n-1) is the square of the determinant of the n X n matrix M_n with elements m(j,k) = cos(Pi*j*k/n). See Zhi-Wei Sun, Petrov link. - Hugo Pfoertner, Sep 19 2021
a(n) is the determinant of the n X n matrix P_n such that, when indexed [0, n), P(0, j) = 1, P(i <= j) = i, and P(i > j) = i-n. - C.S. Elder, Mar 11 2024

Examples

			For n=3, a(3)=9 because there are exactly 9 binary relations on A={1, 2} that are functions, namely: {}, {(1,1)}, {(1,2)}, {(2,1)}, {(2,2)}, {(1,1),(2,1)}, {(1,1),(2,2)}, {(1,2),(2,1)} and {(1,2),(2,2)}. - _Dennis P. Walsh_, Apr 21 2011
G.f. = x + 2*x^2 + 9*x^3 + 64*x^4 + 625*x^5 + 7776*x^6 + 117649*x^7 + ...

References

  • Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, page 169.
  • Jonathan L. Gross and Jay Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 524.
  • Hannes Heikinheimo, Heikki Mannila and Jouni K. Seppnen, Finding Trees from Unordered 01 Data, in Knowledge Discovery in Databases: PKDD 2006, Lecture Notes in Computer Science, Volume 4213/2006, Springer-Verlag. - N. J. A. Sloane, Jul 09 2009
  • Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 63.
  • John Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 128.
  • 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).
  • Richard P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see page 25, Prop. 5.3.2, and p. 37, (5.52).

Links

Crossrefs

Cf. A000055, A000081, A000142, A000272, A000312, A002720, A007778, A007830, A008785-A008791, A055860, A002061, A052746, A052756, A052764, A052789, A051129, A098686, A247363, A055302, A248120, A130293, A053506-A053509, A262974.
Other classes of endofunctions: A275549-A275558.

Programs

  • Haskell
    a000169 n = n ^ (n - 1)  -- Reinhard Zumkeller, Sep 14 2014
  • Magma
    [n^(n-1): n in [1..20]]; // Vincenzo Librandi, Jul 17 2015
  • Maple
    A000169 := n -> n^(n-1);
# second program:
spec := [A, {A=Prod(Z, Set(A))}, labeled]; [seq(combstruct[count](spec, size=n), n=1..20)];
# third program:
A000169 := n -> add((-1)^(n+k-1)*pochhammer(n, k)*Stirling2(n-1, k), k = 0..n-1):
seq(A000169(n), n = 1 .. 23);  # Mélika Tebni, May 07 2023
  • Mathematica
    Table[n^(n - 1), {n, 1, 20}] (* Stefan Steinerberger, Apr 01 2006 *)
Range[0, 18]! CoefficientList[ Series[ -LambertW[-x], {x, 0, 18}], x] // Rest (* Robert G. Wilson v, updated by Jean-François Alcover, Oct 14 2019 *)
(* Next, a signed version A000169 from the Vandermonde determinant of (1,1/2,...,1/n) *)
f[j_] := 1/j; z = 12;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}]
Table[v[n], {n, 1, z}]
1/%  (* A203421 *)
Table[v[n]/v[n + 1], {n, 1, z - 1}]  (* A000169 signed *)
(* Clark Kimberling, Jan 02 2012 *)
a[n_]:=Det[Table[If[i==0,1,If[i<=j,i,i-n]],{i,0,n-1},{j,0,n-1}]]; Array[a,20] (* Stefano Spezia, Mar 12 2024 *)
  • MuPAD
    n^(n-1) $ n=1..20 /* Zerinvary Lajos, Apr 01 2007 */
  • PARI
    a(n) = n^(n-1)
  • Python
    def a(n): return n**(n-1)
print([a(n) for n in range(1, 21)]) # Michael S. Branicky, Sep 19 2021
  • Python
    from sympy import Matrix
def P(n): return [[ (i-n if i > j else i) + (i == 0) for j in range(n) ] for i in range(n)]
print(*(Matrix(P(n)).det() for n in range(1, 21)), sep=', ') # C.S. Elder, Mar 12 2024

Formula

The e.g.f. T(x) = Sum_{n>=1} n^(n-1)*x^n/n! satisfies T(x) = x*exp(T(x)), so T(x) is the functional inverse (series reversion) of x*exp(-x).
Also T(x) = -LambertW(-x) where W(x) is the principal branch of Lambert's function.
T(x) is sometimes called Euler's tree function.
a(n) = A000312(n-1)*A128434(n,1)/A128433(n,1). - Reinhard Zumkeller, Mar 03 2007
E.g.f.: LambertW(x)=x*G(0); G(k) = 1 - x*((2*k+2)^(2*k))/(((2*k+1)^(2*k)) - x*((2*k+1)^(2*k))*((2*k+3)^(2*k+1))/(x*((2*k+3)^(2*k+1)) - ((2*k+2)^(2*k+1))/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Dec 30 2011
a(n) = Sum_{i=1..n} binomial(n-1,i-1)*i^(i-2)*(n-i)^(n-i). - Dmitry Kruchinin, Oct 28 2013
Limit_{n->oo} a(n)/A000312(n-1) = e. - Daniel Suteu, Jul 23 2016
From Amiram Eldar, Nov 20 2020: (Start)
Sum_{n>=1} 1/a(n) = A098686.
Sum_{n>=1} (-1)^(n+1)/a(n) = A262974. (End)
a(n) = Sum_{k=0..n-1} (-1)^(n+k-1)*Pochhammer(n, k)*Stirling2(n-1, k). - Mélika Tebni, May 07 2023
In terms of Eulerian numbers A340556(n,k) of the second order Sum_{m>=1} m^(m+n) z^m/m! = 1/(1-T(z))^(2n+1) * Sum_{k=0..n} A2(n,k) T(z)^k. - Marko Riedel, Jan 10 2024

A093883 Product of all possible sums of two distinct numbers taken from among first n natural numbers.

Original entry on oeis.org

1, 3, 60, 12600, 38102400, 2112397056000, 2609908810629120000, 84645606509847871488000000, 82967862872337478796810649600000000, 2781259372192376861719959017613164544000000000
Offset: 1

Views

Author

Amarnath Murthy, Apr 22 2004

Keywords

Comments

From Clark Kimberling, Jan 02 2013: (Start)
Each term divides its successor, as in A006963, and by the corresponding superfactorial, A000178(n), as in A203469.
Abbreviate "Vandermonde" as V. The V permanent of a set S={s(1),s(2),...,s(n)} is a product of sums s(j)+s(k) in analogy to the V determinant as a product of differences s(k)-s(j). Let D(n) and P(n) denote the V determinant and V permanent of S, and E(n) the V determinant of the numbers s(1)^2, s(2)^2, ..., s(n)^2; then P(n) = E(n)/D(n). This is one of many divisibility properties associated with V determinants and permanents. Another is that if S consists of distinct positive integers, then D(n) divides D(n+1) and P(n) divides P(n+1).
Guide to related sequences:
...
s(n).............. D(n)....... P(n)
n................. A000178.... (this)
n+1............... A000178.... A203470
n+2............... A000178.... A203472
n^2............... A202768.... A203475
2^(n-1)........... A203303.... A203477
2^n-1............. A203305.... A203479
n!................ A203306.... A203482
n(n+1)/2.......... A203309.... A203511
Fibonacci(n+1).... A203311.... A203518
prime(n).......... A080358.... A203521
odd prime(n)...... A203315.... A203524
nonprime(n)....... A203415.... A203527
composite(n)...... A203418.... A203530
2n-1.............. A108400.... A203516
n+floor(n/2)...... A203430
n+floor[(n+1)/2].. A203433
1/n............... A203421
1/(n+1)........... A203422
1/(2n)............ A203424
1/(2n+2).......... A203426
1/(3n)............ A203428
Generalizing, suppose that f(x,y) is a function of two variables and S=(s(1),s(2),...s(n)). The phrase, "Vandermonde sequence using f(x,y) applied to S" means the sequence a(n) whose n-th term is the product f(s(j,k)) : 1<=j
...
If f(x,y) is a (bivariate) cyclotomic polynomial and S is a strictly increasing sequence of positive integers, then a(n) consists of integers, each of which divides its successor. Guide to sequences for which f(x,y) is x^2+xy+y^2 or x^2-xy+y^2 or x^2+y^2:
...
s(n) ............ x^2+xy+y^2.. x^2-xy+y^2.. x^2+y^2
n ............... A203012..... A203312..... A203475
n+1 ............. A203581..... A203583..... A203585
2n-1 ............ A203514..... A203587..... A203589
n^2 ............. A203673..... A203675..... A203677
2^(n-1) ......... A203679..... A203681..... A203683
n! .............. A203685..... A203687..... A203689
n(n+1)/2 ........ A203691..... A203693..... A203695
Fibonacci(n) .... A203742..... A203744..... A203746
Fibonacci(n+1) .. A203697..... A203699..... A203701
prime(n) ........ A203703..... A203705..... A203707
floor(n/2) ...... A203748..... A203752..... A203773
floor((n+1)/2) .. A203759..... A203763..... A203766
For f(x,y)=x^4+y^4, see A203755 and A203770. (End)

Examples

			a(4) = (1+2)*(1+3)*(1+4)*(2+3)*(2+4)*(3+4) = 12600.

References

  • Amarnath Murthy, Another combinatorial approach towards generalizing the AM-GM inequality, Octagon Mathematical Magazine, Vol. 8, No. 2, October 2000.
  • Amarnath Murthy, Smarandache Dual Symmetric Functions And Corresponding Numbers Of The Type Of Stirling Numbers Of The First Kind. Smarandache Notions Journal, Vol. 11, No. 1-2-3 Spring 2000.

Links

Crossrefs

Cf. A006963, A093884, A203469.

Programs

  • Maple
    a:= n-> mul(mul(i+j, i=1..j-1), j=2..n):
seq(a(n), n=1..12);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    f[n_] := Product[(j + k), {k, 2, n}, {j, 1, k - 1}]; Array[f, 10] (* Robert G. Wilson v, Jan 08 2013 *)
  • PARI
    A093883(n)=prod(i=1,n,(2*i-1)!/i!)  \\ M. F. Hasler, Nov 02 2012

Formula

Partial products of A006963: a(n) = Product((2*i-1)!/i!, i=1..n). - Vladeta Jovovic, May 27 2004
G.f.: G(0)/(2*x) -1/x, where G(k)= 1 + 1/(1 - 1/(1 + 1/((2*k+1)!/(k+1)!)/x/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 15 2013
a(n) ~ sqrt(A/Pi) * 2^(n^2 + n/2 - 7/24) * exp(-3*n^2/4 + n/2 - 1/24) * n^(n^2/2 - n/2 - 11/24), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Jan 26 2019

Extensions

More terms from Vladeta Jovovic, May 27 2004

A203424 Reciprocal of Vandermonde determinant of (1/2,1/4,...,1/(2n)).

Original entry on oeis.org

1, -4, -144, 73728, 737280000, -183458856960000, -1381360067999170560000, 370806019753548356895375360000, 4086267719027580129096614223921807360000, -2092169072142121026097466482647965368320000000000000
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Comments

Each term divides its successor, as in A203425.

Links

Crossrefs

Cf. A203425, A203421.

Programs

  • Magma
    BarnesG:= func< n | (&*[Factorial(k): k in [0..n-2]]) >;
A203424:= func< n| (-2)^Binomial(n, 2)*(Factorial(n))^n/BarnesG(n+2) >;
[A203424(n): n in [1..20]]; // G. C. Greubel, Dec 07 2023
  • Mathematica
    (* First program *)
f[j_] := 1/(2 j); z = 16;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}];
1/Table[v[n], {n, z}]             (* A203424 *)
Table[v[n]/(4 v[n + 1]), {n, z}]  (* A203425 *)
(* Second program *)
Table[(-2)^Binomial[n,2]*(n!)^n/BarnesG[n+2], {n,20}] (* G. C. Greubel, Dec 07 2023 *)
  • PARI
    a(n) = prod(k=2,n, (-k)^(k-1)) << binomial(n,2); \\ Kevin Ryde, May 03 2022
  • SageMath
    def BarnesG(n): return product(factorial(k) for k in range(n-1))
def A203424(n): return (-2)^binomial(n, 2)*(gamma(n+1))^n/BarnesG(n+2)
[A203424(n) for n in range(1, 21)] # G. C. Greubel, Dec 07 2023

Formula

a(n) = Product_{k=1..n} (-2k)^(k-1). - Andrei Asinowski, Nov 03 2015
a(n) ~ (-1)^(n*(n-1)/2) * A * 2^(n^2/2 - n/2 - 1/2) * n^(n^2/2 - n/2 - 5/12) / (sqrt(Pi) * exp(n^2/4-n)), where A = A074962 is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Dec 05 2015
a(n) = 2^binomial(n,2) * A203421(n). - Kevin Ryde, May 03 2022
a(n) = (-2)^binomial(n,2) * (n!)^n / BarnesG(n+2). - G. C. Greubel, Dec 07 2023

A203422 Reciprocal of Vandermonde determinant of (1/2,1/3,...,1/(n+1)).

Original entry on oeis.org

1, -6, -288, 144000, 933120000, -94097687040000, -172670008499896320000, 6607002383077924814192640000, 5946302144770132332773376000000000000, -140210694122490812598274255654748160000000000000
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Comments

Each term divides its successor, as in A203423.

Links

Crossrefs

Cf. A203421, A203423.

Programs

  • Magma
    BarnesG:= func< n | (&*[Factorial(k): k in [0..n-2]]) >;
A203422:= func< n | (-1)^Binomial(n,2)*Factorial(n)*(Factorial(n+1))^n/BarnesG(n+3) >;
[A203422(n): n in [1..20]]; // G. C. Greubel, Dec 08 2023
  • Mathematica
    (* First program *)
f[j_] := 1/(j + 1); z = 16;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}]
1/Table[v[n], {n, z}]             (* A203422 *)
Table[v[n]/(2 v[n + 1]), {n, z}]  (* A203423 *)
(* Second program *)
Table[(-1)^Binomial[n,2]*n!*(Gamma[n+2])^n/BarnesG[n+3], {n,20}] (* G. C. Greubel, Dec 08 2023 *)
  • PARI
    a(n) = my(f=n+1); prod(i=-n,-2, f*=i); \\ Kevin Ryde, Apr 17 2022
  • SageMath
    def BarnesG(n): return product(factorial(k) for k in range(n-1))
def A203422(n): return (-1)^binomial(n,2)*gamma(n+1)*(gamma(n+2))^n/BarnesG(n+3)
[A203422(n) for n in range(1, 21)] # G. C. Greubel, Dec 08 2023

Formula

a(n) = (n+1)^(n-1) * Product_{i=2..n} (-i)^(i-1). - Kevin Ryde, Apr 17 2022
a(n) = (-1)^binomial(n,2) * n! * (Gamma(n+2))^n / BarnesG(n+3). - G. C. Greubel, Dec 08 2023
a(n) ~ (-1)^(n*(n-1)/2) * A * n^(n*(n+1)/2 - 17/12) / (sqrt(2*Pi) * exp(n^2/4 - n - 1)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Aug 09 2025

A203426 Reciprocal of Vandermonde determinant of (1/4,1/6,...,1/(2n+2)).

Original entry on oeis.org

1, -12, -2304, 9216000, 955514880000, -3083393008926720000, -362115253665574567280640000, 1773553697494609431031516590243840000, 408626771902758012909661422392180736000000000000, -4933225232839126697329071833709661506078108549120000000000000
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Comments

Each term divides its successor, as in A203427.

Links

Crossrefs

Cf. A203421, A203424, A203427.

Programs

  • Magma
    BarnesG:= func< n | (&*[Factorial(k): k in [0..n-2]]) >;
A203426:= func< n | (-2)^Binomial(n,2)*Factorial(n)*(Factorial(n+1))^n/BarnesG(n+3) >;
[A203426(n): n in [1..20]]; // G. C. Greubel, Dec 05 2023
  • Maple
    with(LinearAlgebra):
a:= n-> 1/Determinant(VandermondeMatrix([1/(2*i+2)$i=1..n])):
seq(a(n), n=1..12);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    (* First program *)
f[j_] := 1/(2 j + 2); z = 12;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}];
1/Table[v[n], {n, 1, z}]              (* A203426 *)
Table[v[n]/(4 v[n + 1]), {n, 1, z}]   (* A203427 *)
(* Second program *)
Table[(-2)^Binomial[n,2]*n!*(Gamma[n+2])^n/BarnesG[n+3], {n,20}] (* G. C. Greubel, Dec 05 2023 *)
  • SageMath
    def BarnesG(n): return product(factorial(k) for k in range(n-1))
def A203426(n): return (-2)^binomial(n,2)*gamma(n+1)*(gamma(n+2))^n/BarnesG(n+3)
[A203426(n) for n in range(1,21)] # G. C. Greubel, Dec 05 2023

Formula

a(n) = Product_{k=1..n} k * (-2(k+1))^(k-1). - Andrei Asinowski, Nov 03 2015
a(n) ~ (-1)^(n*(n-1)/2) * A * 2^(n^2/2 - n/2 - 1/2) * n^(n^2/2 + n/2 - 17/12) / (sqrt(Pi) * exp(n^2/4 - n - 1)), where A = A074962 is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Dec 05 2015
a(n) = (-2)^binomial(n,2) * n! * (Gamma(n+2))^n / BarnesG(n+3). - G. C. Greubel, Dec 05 2023

A203428 Reciprocal of Vandermonde determinant of (1/3,1/6,...,1/(3n)).

Original entry on oeis.org

1, -6, -486, 839808, 42515280000, -80335512599040000, -6890065294166289123840000, 31601087581187838970614157148160000, 8925080517850366815864624583251321642024960000
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Comments

Each term divides its successor, as in A203429.

Links

Crossrefs

Cf. A203421, A203424, A203429.

Programs

  • Magma
    Barnes:= func< n | (&*[Factorial(j): j in [1..n-1]]) >;
A203428:= func< n | (-3)^Binomial(n,2)*(Factorial(n))^n/Barnes(n+1) >;
[A203428(n): n in [1..25]]; // G. C. Greubel, Sep 28 2023
  • Mathematica
    (* First program *)
f[j_]:= 1/(3*j); z = 16;
v[n_]:= Product[Product[f[k] - f[j], {j,k-1}], {k,2,n}]
1/Table[v[n], {n,z}]             (* A203428 *)
Table[v[n]/(3*v[n+1]), {n,z}]    (* A203429 *)
(* Second program *)
Table[(-3)^Binomial[n,2]*(Gamma[n+1])^(n-1)/BarnesG[n+1], {n,20}] (* G. C. Greubel, Sep 28 2023 *)
  • SageMath
    def barnes(n): return product(factorial(j) for j in range(n))
def A203428(n): return (-3)^binomial(n,2)*(factorial(n))^n/barnes(n+1)
[A203428(n) for n in range(1,21)] # G. C. Greubel, Sep 28 2023

Formula

a(n) = (-3)^binomial(n,2) * (Gamma(n+1))^(n-1) / BarnesG(n+1). - G. C. Greubel, Sep 28 2023
a(n) ~ (-1)^(n*(n-1)/2) * A * 3^(n*(n-1)/2) * n^(n*(n-1)/2 - 5/12) / (sqrt(2*Pi) * exp(n^2/4 - n)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Aug 09 2025

A203423 a(n) = w(n+1)/(2*w(n)), where w=A203422.

Original entry on oeis.org

-3, 24, -250, 3240, -50421, 917504, -19131876, 450000000, -11789738455, 340545503232, -10752962364222, 368510430439424, -13623365478515625, 540431955284459520, -22899384412078526344, 1032236014321051140096, -49323481720063219673451, 2490368000000000000000000, -132484966403310261255807810
Offset: 1

Views

Author

Clark Kimberling, Jan 02 2012

Keywords

Links

Crossrefs

Cf. A000169, A053506, A203421, A203422.

Programs

  • Magma
    [(-1)^n*(n+1)*(n+2)^n/2: n in [1..20]]; // G. C. Greubel, Dec 07 2023
  • Mathematica
    (* First program *)
f[j_] := 1/(j + 1); z = 16;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}]
1/Table[v[n], {n, 1, z}]             (* A203422 *)
Table[v[n]/(2 v[n + 1]), {n, 1, z}]  (* this sequence *)
(* Second program *)
Table[(-1)^n*(n+1)*(n+2)^n/2, {n,20}] (* G. C. Greubel, Dec 07 2023 *)
  • SageMath
    [(-1)^n*(n+1)*(n+2)^n/2 for n in range(1,21)] # G. C. Greubel, Dec 07 2023

Formula

a(n) = (-1)^n*A053506(n+2)/2. - Steven Finch, Apr 16 2022
E.g.f.: -(1/(2*x^2))*( W(x)/(1 + W(x))^3 - 2*W(x)/(1 + W(x)) + W(x) + x^2), where W(x) = LambertW(x). - G. C. Greubel, Dec 07 2023

A367492 a(n) = Product_{k=0..n} (k+1)!^k.

Original entry on oeis.org

1, 2, 72, 995328, 206391214080000, 39934999921327865856000000000, 654541076770994951831125144608178176000000000000000, 113391518341540395635327816456127297986876881699306137641287680000000000000000000000
Offset: 0

Views

Author

Vaclav Kotesovec, Nov 20 2023

Keywords

Links

Crossrefs

Cf. A203421, A255269.

Programs

  • Magma
    [(&*[Factorial(k+1)^k: k in [0..n]]): n in [0..15]]; // G. C. Greubel, Feb 18 2024
  • Mathematica
    Table[Product[(k+1)!^k, {k, 0, n}], {n, 0, 10}]
  • SageMath
    [product(factorial(k+1)^k for k in range(n+1)) for n in range(16)] # G. C. Greubel, Feb 18 2024

Formula

a(n) ~ A^(3/2) * n^(n^3/3 + 5*n^2/4 + 11*n/12 - 3/8) * (2*Pi)^(n^2/4 + n/4 - 1/2) / exp(4*n^3/9 + 7*n^2/8 - n + zeta(3)/(8*Pi^2) - 25/24), where A is the Glaisher-Kinkelin constant A074962.
a(n) = (n+1)^n * abs(A203421(n)) * A255269(n).

A267968 a(n) = Product_{k = 1..n} k^(k + 1).

Original entry on oeis.org

1, 1, 8, 648, 663552, 10368000000, 2902376448000000, 16731622649806848000000, 2245680377810414777401344000000, 7830203310981140781182893575634944000000, 783020331098114078118289357563494400000000000000000, 2457453226667794121573260254679367673480373862400000000000000000
Offset: 0

Views

Author

José María Grau Ribas, Jan 22 2016

Keywords

Links

Crossrefs

Cf. A002109 (Product_{k = 1..n} k^k), A203421 (Product_{k = 1..n} k^(k-1), up to sign).

Programs

  • Magma
    [&*[k^(k+1): k in [1..n]]: n in [1..11]]; // Vincenzo Librandi, Jan 23 2016
  • Maple
    a:= proc(n) a(n):= `if`(n=0, 1, a(n-1)*n^(n+1)) end:
seq(a(n), n=0..12);  # Alois P. Heinz, Feb 10 2016
  • Mathematica
    a[n_]:= Product[k^(k+1), {k,n}]; Table[a[n], {n, 0, 20}]
Table[Hyperfactorial[n]*n!, {n, 0, 15}] (* Vaclav Kotesovec, Jan 26 2016 *)
  • PARI
    a(n) = prod(k=1, n, k^(k+1)); \\ Michel Marcus, Jan 23 2016
  • SageMath
    [product(k^(k+1) for k in range(1,n+1)) for n in range(21)] # G. C. Greubel, Feb 18 2024

Formula

a(n) = n! * A002109(n). - Vaclav Kotesovec, Jan 26 2016
a(n) = (n!)^2 * abs(A203421(n)). - Michel Marcus, Feb 11 2016
Showing 1-9 of 9 results.

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