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.

Previous Showing 41-50 of 176 results. Next

A007557 Shifts left when inverse Moebius transform applied twice.

Original entry on oeis.org

1, 1, 3, 5, 10, 12, 24, 26, 43, 52, 78, 80, 133, 135, 189, 219, 295, 297, 428, 430, 584, 642, 804, 806, 1100, 1123, 1395, 1494, 1856, 1858, 2428, 2430, 2977, 3143, 3739, 3811, 4790, 4792, 5654, 5930, 7072, 7074, 8656
Offset: 1

Views

Author

Keywords

Comments

Equals eigensequence of triangle A127170 (the square of the inverse Mobius transform). - Gary W. Adamson, Apr 27 2009

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Mathematica
    a[n_] := a[n] = Sum[ DivisorSigma[0, (n - 1)/d]*a[d], {d, Divisors[n - 1]}]; a[1] = 1; Table[a[n], {n, 1, 43}] (* Jean-François Alcover, Dec 12 2011, after Vladeta Jovovic *)

Formula

a(n+1) = Sum_{d divides n} tau(n/d)*a(d). - Vladeta Jovovic, Jan 24 2003
From Ilya Gutkovskiy, Apr 30 2019: (Start)
G.f. A(x) satisfies: A(x) = x * (1 + Sum_{i>=1} Sum_{j>=1} A(x^(i*j))).
G.f.: A(x) = Sum_{n>=1} a(n)*x^n = x * (1 + Sum_{i>=1} Sum_{j>=1} a(i)*x^(i*j)/(1 - x^(i*j))). (End)

Extensions

More terms from Vladeta Jovovic, Jan 24 2003

A007558 Shifts 2 places left when e.g.f. is squared.

Original entry on oeis.org

1, 1, 1, 2, 4, 10, 30, 100, 380, 1600, 7400, 37400, 204600, 1205600, 7612000, 51260000, 366784000, 2778820000, 22222332000, 187067320000, 1653461480000, 15310662400000, 148217381840000, 1497226615280000, 15754506226800000, 172407188412800000
Offset: 0

Views

Author

Keywords

References

  • O Bodini, M Dien, X Fontaine, A Genitrini, H K Hwang, Increasing Diamonds, in LATIN 2016: 12th Latin American Symposium, Ensenada, Mexico, April 11-15, 2016, Proceedings Pages pp 207-219 2016 DOI 10.1007/978-3-662-49529-2_16 Lecture Notes in Computer Science Series Volume 9644
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Maple
    a:= proc(n) option remember;
          `if`(n<2, 1, add(a(i)*a(n-2-i) *binomial(n-2, i), i=0..n-2))
        end:
    seq(a(n), n=0..30);  # Alois P. Heinz, Jun 22 2012
  • Mathematica
    a[n_] := a[n] = If[n < 2, 1, Sum[a[i] * a[n - 2 - i] * Binomial[n - 2, i], {i, 0, n - 2}]]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Feb 03 2014, after Alois P. Heinz *)
    Table[SeriesCoefficient[1 + (18 (WeierstrassP[x, {0, -1/108}] - WeierstrassPPrime[x, {0, -1/108}]))/(6 WeierstrassP[x, {0, -1/108}] - 1)^2, {x, 0, k}] k!, {k, 0, 30}] (* Jan Mangaldan, Nov 27 2020 *)

Formula

a(n) ~ c * d^n * n! * n, where d = 0.42089835222875301896706732846764190595145230471243866202153775712470703269... is the root of the equation WeierstrassP(1/d, 0, -1/108) = 1/6 and c = 1.06293253745327664869312823202016275205862332741406172188742740834633... - Vaclav Kotesovec, Sep 06 2014, updated Nov 27 2020
E.g.f.: 6^(1/3) * WeierstrassP((x+c)/6^(1/3), 0, -1/3), where c = 9.1898572290187191497581591181140131456801040793456712149069964791654... is the root of the equation WeierstrassP(c/6^(1/3), 0, -1/3) = 6^(-1/3). - Vaclav Kotesovec, Jun 14 2015
E.g.f. A(x) satisfies: A(x) = 1 + x + Integral(Integral A(x)^2 dx) dx. - Ilya Gutkovskiy, Jul 04 2020

A295739 Expansion of e.g.f. exp(Sum_{k>=1} d(k)*x^k/k!), where d(k) is the number of divisors of k (A000005).

Original entry on oeis.org

1, 1, 3, 9, 36, 158, 802, 4434, 26978, 176637, 1243528, 9316519, 74065506, 621187700, 5480130494, 50662481722, 489552042241, 4931215686119, 51668848043427, 561981734692781, 6333882472789914, 73850048237680936, 889461218944314524, 11051067390893340510
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 26 2017

Keywords

Comments

Exponential transform of A000005.

Crossrefs

Programs

  • Maple
    a:=series(exp(add(tau(k)*x^k/k!,k=1..100)),x=0,24): seq(n!*coeff(a,x,n),n=0..23); # Paolo P. Lava, Mar 27 2019
  • Mathematica
    nmax = 23; CoefficientList[Series[Exp[Sum[DivisorSigma[0, k] x^k/k!, {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = Sum[Binomial[n - 1, k - 1] DivisorSigma[0, k] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[n], {n, 0, 23}]

Formula

E.g.f.: exp(Sum_{k>=1} A000005(k)*x^k/k!).
a(0) = 1; a(n) = Sum_{k=1..n} binomial(n-1,k-1)*A000005(k)*a(n-k).

A000996 Shifts 3 places left under binomial transform.

Original entry on oeis.org

1, 0, 0, 1, 1, 1, 2, 6, 17, 44, 112, 304, 918, 3040, 10623, 38161, 140074, 528594, 2068751, 8436893, 35813251, 157448068, 713084042, 3315414747, 15805117878, 77273097114, 387692392570, 1996280632656, 10542604575130, 57034787751655, 315649657181821
Offset: 0

Views

Author

Keywords

References

  • 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).

Crossrefs

Column k=3 of A143983.

Programs

  • Maple
    a:= proc(n) option remember; local k; if n<=2 then [1,0,0][n+1] else 1+ add(binomial(n-3,k) *a(k), k=3..n-3) fi end: seq(a(n), n=0..29); # Alois P. Heinz, Sep 05 2008
  • Mathematica
    a[n_] := a[n] = If[n <= 2 , {1, 0, 0}[[n+1]], 1+Sum [Binomial[n-3, k]*a[k], {k, 3, n-3}]]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Mar 24 2014, after Alois P. Heinz *)

Formula

G.f. A(x) satisfies: A(x) = 1 + x^3 * A(x/(1 - x)) / (1 - x). - Ilya Gutkovskiy, Aug 09 2020

Extensions

More terms from Alois P. Heinz, Sep 05 2008

A007549 Number of increasing rooted connected graphs where every block is a complete graph.

Original entry on oeis.org

1, 1, 3, 14, 89, 716, 6967, 79524, 1041541, 15393100, 253377811, 4596600004, 91112351537, 1959073928124, 45414287553455, 1129046241331316, 29965290866974493, 845605519848379436, 25282324544244718411, 798348403914242674980, 26549922456617388029641
Offset: 1

Views

Author

Keywords

Comments

In an increasing rooted graph, nodes are numbered and the numbers increase as you move away from the root.
(a(n+1)/a(n))/n tends to 1/A073003 = 1.676875... (same limit as A029768). - Vaclav Kotesovec, Jul 26 2014

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A029768.
Row sums of A078341. Column k=1 of A264436.

Programs

  • Maple
    exptr:= proc(p) local g; g:= proc(n) option remember; p(n) +add(binomial(n-1, k-1) *p(k) *g(n-k), k=1..n-1) end: end: b:= exptr(exptr(a)): a:= n-> `if`(n=0, 1, b(n-1)): seq(a(n), n=1..30); # Alois P. Heinz, Oct 07 2008
  • Mathematica
    exptr[p_] := Module[{g}, g[n_] := g[n] = p[n] + Sum[ Binomial[n-1, k-1]*p[k]*g[n-k], {k, 1, n-1}]; g]; b = exptr[ exptr[a] ]; a[n_] := If[n == 0, 1, b[n-1]]; Table[ a[n], {n, 1, 19}] (* Jean-François Alcover, May 10 2012, after Alois P. Heinz *)

Formula

Shifts left when exponentiated twice.
Conjecture: a(n) = Sum_{i=0..2^(n-2) - 1} b(i) for n > 1 with a(1) = 1 where b(n) = (L(n) + 2)*b(f(n)) + Sum_{k=0..L(n) - 1} (1 - R(n,k))*b(f(n) + 2^k*(1 - R(n,k))) for n > 0 with b(0) = 1, L(n) = A000523(n), f(n) = A053645(n) and where R(n,k) = floor(n/2^k) mod 2. Here R(n,k) is the (k+1)-th bit from the right side in the binary expansion of n. - Mikhail Kurkov, Jul 21 2024
Conjecture: a(n) = D^(n-1)(exp(x)) evaluated at x = 0, where D denotes the operator exp(x)*(1 + x)*d/dx. - Peter Bala, Feb 24 2025

Extensions

New description from Christian G. Bower, Oct 15 1998

A278768 Expansion of Product_{k>=1} 1/(1 - x^k)^(k*(3*k-1)/2).

Original entry on oeis.org

1, 1, 6, 18, 55, 150, 424, 1113, 2923, 7401, 18510, 45271, 109297, 259447, 608428, 1407958, 3222132, 7292198, 16340830, 36265672, 79775931, 173999194, 376497975, 808471181, 1723592762, 3649271887, 7675809680, 16043777217, 33332888108, 68853608216, 141438908854, 288994878713, 587458691042
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 28 2016

Keywords

Comments

Euler transform of the pentagonal numbers (A000326).

Crossrefs

Programs

  • Maple
    with(numtheory):
    a:= proc(n) option remember; `if`(n=0, 1, add(add(
          d^2*(3*d-1)/2, d=divisors(j))*a(n-j), j=1..n)/n)
        end:
    seq(a(n), n=0..35);  # Alois P. Heinz, Dec 02 2016
  • Mathematica
    nmax=32; CoefficientList[Series[Product[1/(1 - x^k)^(k (3 k - 1)/2), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - x^k)^(k*(3*k-1)/2).
a(n) ~ exp(-Zeta'(-1)/2 - 3*Zeta(3)/(8*Pi^2) - 25*Zeta(3)^3/(6*Pi^8) - 5^(5/4)*Zeta(3)^2/(2^(7/4)*Pi^5) * n^(1/4) - sqrt(5/2)*Zeta(3)/Pi^2 * sqrt(n) + 2^(7/4)*Pi/(3*5^(1/4)) * n^(3/4)) / (2^(155/96) * 5^(11/96) * Pi^(1/24) * n^(59/96)). - Vaclav Kotesovec, Dec 02 2016

A280950 Expansion of Product_{k>=0} 1/(1 - x^(3*k*(k+1)/2+1)).

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 9, 11, 11, 12, 13, 15, 15, 16, 17, 19, 20, 22, 24, 26, 27, 29, 31, 33, 34, 37, 40, 43, 45, 48, 51, 54, 56, 60, 63, 67, 70, 76, 80, 84, 87, 93, 97, 102, 106, 113, 118, 125, 130, 138, 143, 151, 157, 166, 172, 181, 189, 200, 207, 217, 225, 237, 245, 257, 267, 280
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 11 2017

Keywords

Comments

Number of partitions of n into centered triangular numbers (A005448).

Examples

			a(8) = 3 because we have [4, 4], [4, 1, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1].
		

Crossrefs

Programs

  • Maple
    N:= 100:
    kmax:= floor((sqrt(24*N-15)-3)/6):
    S:= series(mul(1/(1-x^(3*k*(k+1)/2+1)),k=0..kmax),x,N+1):
    seq(coeff(S,x,j),j=0..N); # Robert Israel, Jan 25 2017
  • Mathematica
    nmax = 78; CoefficientList[Series[Product[1/(1 - x^(3 k (k + 1)/2 + 1)), {k, 0, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=0} 1/(1 - x^(3*k*(k+1)/2+1)).

A294102 Expansion of Product_{k>=1} (1 + x^k)^(k*(3*k-1)/2).

Original entry on oeis.org

1, 1, 5, 17, 44, 127, 332, 866, 2182, 5412, 13119, 31292, 73516, 170136, 388829, 877653, 1959111, 4327221, 9464856, 20511598, 44067446, 93901142, 198539477, 416696608, 868448305, 1797890682, 3698350956, 7561361750, 15369154555, 31064311255, 62449795986, 124895635385, 248538538858, 492207649241
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 09 2017

Keywords

Comments

Weigh transform of the pentagonal numbers (A000326).
This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = -n*(3*n-1)/2, g(n) = -1. - Seiichi Manyama, Nov 14 2017

Crossrefs

Programs

  • Mathematica
    nmax = 33; CoefficientList[Series[Product[(1 + x^k)^(k (3 k - 1)/2), {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d^2 (3 d - 1)/2, {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 33}]

Formula

G.f.: Product_{k>=1} (1 + x^k)^A000326(k).
a(n) ~ exp(-225*Zeta(3)^3 / (98*Pi^8) - 9 * 5^(5/4) * Zeta(3)^2 / (4 * 7^(5/4) * Pi^5) * n^(1/4) - (3*sqrt(5/7) * Zeta(3) / (2*Pi^2)) * sqrt(n) + (2 * (7/5)^(1/4) * Pi / 3) * n^(3/4)) * 7^(1/8) / (2^(47/24) * 5^(1/8) * n^(5/8)). - Vaclav Kotesovec, Nov 10 2017
a(0) = 1 and a(n) = (1/(2*n)) * Sum_{k=1..n} b(k)*a(n-k) where b(n) = Sum_{d|n} d^2*(3*d-1)*(-1)^(1+n/d). - Seiichi Manyama, Nov 14 2017

A294837 Expansion of Product_{k>=1} (1 + x^k)^(k*(5*k-3)/2).

Original entry on oeis.org

1, 1, 7, 25, 73, 236, 688, 1994, 5573, 15272, 40896, 107526, 277999, 707209, 1774067, 4390665, 10734216, 25941541, 62022609, 146793160, 344129900, 799517074, 1841734224, 4208327222, 9542121050, 21477834062, 48005313446, 106579556936, 235107392079, 515441826521, 1123360284127, 2434346065621
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 09 2017

Keywords

Comments

Weigh transform of the heptagonal numbers (A000566).
This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = -n*(5*n-3)/2, g(n) = -1. - Seiichi Manyama, Nov 14 2017

Crossrefs

Programs

  • Mathematica
    nmax = 31; CoefficientList[Series[Product[(1 + x^k)^(k (5 k - 3)/2), {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d^2 (5 d - 3)/2, {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 31}]

Formula

G.f.: Product_{k>=1} (1 + x^k)^A000566(k).
a(n) ~ 7^(1/8) * exp(2*Pi*7^(1/4) * n^(3/4) / 3^(5/4) - 9*Zeta(3) * sqrt(3*n/7) /(2*Pi^2) - 243*Zeta(3)^2 * (3*n/7)^(1/4) / (28*Pi^5) - 2187*Zeta(3)^3 / (98*Pi^8)) / (2^(15/8) * 3^(1/8) * n^(5/8)). - Vaclav Kotesovec, Nov 10 2017
a(0) = 1 and a(n) = (1/(2*n)) * Sum_{k=1..n} b(k)*a(n-k) where b(n) = Sum_{d|n} d^2*(5*d-3)*(-1)^(1+n/d). - Seiichi Manyama, Nov 14 2017

A294838 Expansion of Product_{k>=1} (1 + x^k)^(k*(3*k-2)).

Original entry on oeis.org

1, 1, 8, 29, 89, 301, 915, 2763, 8040, 22910, 63776, 174174, 467448, 1233836, 3209679, 8234149, 20857621, 52206847, 129227514, 316543962, 767767628, 1844925743, 4394337797, 10379319118, 24320964976, 56557678603, 130571770387, 299357973400, 681777058604, 1542840256421, 3470045577372
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 09 2017

Keywords

Comments

Weigh transform of the octagonal numbers (A000567).
This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = -n*(3*n-2), g(n) = -1. - Seiichi Manyama, Nov 14 2017

Crossrefs

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[Product[(1 + x^k)^(k (3 k - 2)), {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d^2 (3 d - 2), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 30}]

Formula

G.f.: Product_{k>=1} (1 + x^k)^A000567(k).
a(n) ~ exp(-1800*Zeta(3)^3 / (49*Pi^8) - (9 * 2^(3/4) * 5^(5/4) * Zeta(3)^2 / (7^(5/4)*Pi^5)) * n^(1/4) - (3*sqrt(10/7) * Zeta(3) / Pi^2) * sqrt(n) + (2*(14/5)^(1/4) * Pi/3) * n^(3/4)) * 7^(1/8) / (2^(41/24) * 5^(1/8) * n^(5/8)). - Vaclav Kotesovec, Nov 10 2017
a(0) = 1 and a(n) = (1/n) * Sum_{k=1..n} b(k)*a(n-k) where b(n) = Sum_{d|n} d^2*(3*d-2)*(-1)^(1+n/d). - Seiichi Manyama, Nov 14 2017
Previous Showing 41-50 of 176 results. Next