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.

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A280951 Expansion of Product_{k>=0} 1/(1 - x^(2*k*(k+1)+1)).

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 8, 8, 10, 11, 11, 12, 12, 14, 15, 15, 16, 16, 18, 19, 19, 21, 22, 24, 26, 26, 28, 29, 31, 33, 33, 35, 36, 39, 42, 43, 45, 47, 50, 53, 54, 56, 58, 61, 65, 66, 69, 72, 76, 81, 83, 86, 89, 93, 98, 100, 103, 107, 112, 118, 121, 125, 130, 136, 142, 146
Offset: 0

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Author

Ilya Gutkovskiy, Jan 11 2017

Keywords

Comments

Number of partitions of n into centered square numbers (A001844).

Examples

			a(10) = 3 because we have [5, 5], [5, 1, 1, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1, 1, 1].
		

Crossrefs

Programs

  • Mathematica
    nmax = 82; CoefficientList[Series[Product[1/(1 - x^(2 k (k + 1) + 1)), {k, 0, nmax}], {x, 0, nmax}], x]

Formula

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

A280952 Expansion of Product_{k>=0} 1/(1 - x^(5*k*(k+1)/2+1)).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 7, 7, 7, 7, 8, 8, 9, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16, 16, 17, 18, 19, 19, 20, 21, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 37, 38, 40, 42, 44, 45, 47, 49, 51, 53, 55, 56, 58, 60, 62, 64, 67, 68, 71, 74, 77, 79, 83, 85, 88, 91, 94, 96, 100
Offset: 0

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Author

Ilya Gutkovskiy, Jan 11 2017

Keywords

Comments

Number of partitions of n into centered pentagonal numbers (A005891).

Examples

			a(12) = 3 because we have [6, 6], [6, 1, 1, 1, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1].
		

Crossrefs

Programs

  • Maple
    h:= proc(n) option remember; `if`(n<0, 0, (t->
          `if`(((t+1)*5*t+2)/2>n, t-1, t))(1+h(n-1)))
        end:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<0, 0,
          b(n, i-1)+(t-> b(n-t, min(i, h(n-t))))(((i+1)*5*i+2)/2)))
        end:
    a:= n-> b(n, h(n)):
    seq(a(n), n=0..100);  # Alois P. Heinz, Dec 28 2018
  • Mathematica
    nmax = 88; CoefficientList[Series[Product[1/(1 - x^(5 k (k + 1)/2 + 1)), {k, 0, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=0} 1/(1 - x^(5*k*(k+1)/2+1)).

A280953 Expansion of Product_{k>=0} 1/(1 - x^(3*k*(k+1)+1)).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 7, 7, 8, 8, 9, 9, 10, 11, 11, 12, 12, 13, 13, 14, 15, 15, 16, 16, 17, 17, 18, 19, 19, 20, 20, 22, 23, 24, 25, 25, 27, 27, 29, 30, 31, 32, 32, 34, 34, 36, 37, 38, 39, 40, 43, 44, 46, 47, 48, 50, 51, 54, 55, 57, 58, 59
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 11 2017

Keywords

Comments

Number of partitions of n into centered hexagonal numbers (A003215).

Examples

			a(14) = 3 because we have [7, 7], [7, 1, 1, 1, 1, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1].
		

Crossrefs

Programs

  • Maple
    h:= proc(n) option remember; `if`(n<0, 0, (t->
          `if`(3*t*(t+1)+1>n, t-1, t))(1+h(n-1)))
        end:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<0, 0,
          b(n, i-1)+(t-> b(n-t, min(i, h(n-t))))(3*i*(i+1)+1)))
        end:
    a:= n-> b(n, h(n)):
    seq(a(n), n=0..100);  # Alois P. Heinz, Dec 28 2018
  • Mathematica
    nmax = 86; CoefficientList[Series[Product[1/(1 - x^(3 k (k + 1) + 1)), {k, 0, nmax}], {x, 0, nmax}], x]

Formula

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

A281156 Expansion of Product_{k>=1} (1 + x^k)^(k*(k+1)*(2*k+1)/6).

Original entry on oeis.org

1, 1, 5, 19, 54, 165, 467, 1317, 3599, 9687, 25519, 66203, 169254, 426750, 1062950, 2616818, 6373911, 15369774, 36716706, 86939235, 204152395, 475631501, 1099874363, 2525418842, 5759549109, 13050991205, 29391523405, 65801951770, 146486952644, 324340095729, 714389015139
Offset: 0

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Author

Ilya Gutkovskiy, Jan 16 2017

Keywords

Comments

Weigh transform of square pyramidal numbers (A000330).

Crossrefs

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[Product[(1 + x^k)^(k (k + 1) (2 k + 1)/6), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} (1 + x^k)^(k*(k+1)*(2*k+1)/6).
a(n) ~ exp(5*(15*Zeta(5))^(1/5) * n^(4/5) / 2^(11/5) + 7*Pi^4 * n^(3/5) / (360*2^(2/5) * (15*Zeta(5))^(3/5)) + (Zeta(3) / (2^(13/5) * (15*Zeta(5))^(2/5)) - 49*Pi^8 / (2160000 * 2^(3/5) * 15^(2/5) * Zeta(5)^(7/5)))*n^(2/5) + (343*Pi^12 / (9720000000 * 2^(4/5) * 15^(1/5) * Zeta(5)^(11/5)) - 7*Pi^4 * Zeta(3) / (18000 * 2^(4/5) * 15^(1/5) * Zeta(5)^(6/5))) * n^(1/5) + 49*Pi^8 * Zeta(3) / (129600000 * Zeta(5)^2) - 2401 * Pi^16 / (83980800000000 * Zeta(5)^3) - Zeta(3)^2 / (1200*Zeta(5))) * (3*Zeta(5))^(1/10) / (2^(11/18) * 5^(2/5) * sqrt(Pi) * n^(3/5)). - Vaclav Kotesovec, Nov 09 2017

A294836 Expansion of Product_{k>=1} (1 + x^k)^(k*(2*k-1)).

Original entry on oeis.org

1, 1, 6, 21, 58, 178, 494, 1365, 3640, 9533, 24401, 61384, 151958, 370335, 890565, 2113913, 4959199, 11505799, 26420628, 60082005, 135386341, 302448477, 670148898, 1473387787, 3215519032, 6968266907, 14999453058, 32079714584, 68187859040, 144083404856, 302727633735, 632579826174
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 09 2017

Keywords

Comments

Weigh transform of the hexagonal numbers (A000384).
This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = -n*(2*n-1), g(n) = -1. - Seiichi Manyama, Nov 14 2017

Crossrefs

Programs

  • Mathematica
    nmax = 31; CoefficientList[Series[Product[(1 + x^k)^(k (2 k - 1)), {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d^2 (2 d - 1), {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)^A000384(k).
a(n) ~ 7^(1/8) * exp(Pi*2^(3/2) * (7/15)^(1/4) * n^(3/4)/3 - 3*Zeta(3)*sqrt(15*n/7) / (2*Pi^2) - 135*Zeta(3)^2 * (15*n/7)^(1/4) / (28*sqrt(2)*Pi^5) - 2025*Zeta(3)^3 / (196*Pi^8)) / (2^(5/3) * 15^(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*(2*d-1)*(-1)^(1+n/d). - Seiichi Manyama, Nov 14 2017

A300452 Logarithmic transform of the cubes A000578.

Original entry on oeis.org

0, 1, 7, 5, -146, -351, 9936, 51421, -1394000, -12844287, 328407400, 4874111901, -115361217696, -2607873466511, 55768370301112, 1866984952934445, -34886452149332864, -1720211491314549375, 26716801597874981064, 1979492625918149729437, -23490293022369696366560, -2777285149336544358953679
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 06 2018

Keywords

Examples

			E.g.f.: A(x) = x/1! + 7*x^2/2! + 5*x^3/3! - 146*x^4/4! - 351*x^5/5! + 9936*x^6/6! + ...
		

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; (t-> `if`(n=0, 0, t(n) -add(j*
          binomial(n, j)*t(n-j)*a(j), j=1..n-1)/n))(i->i^3)
        end:
    seq(a(n), n=0..25);  # Alois P. Heinz, Mar 06 2018
  • Mathematica
    nmax = 21; CoefficientList[Series[Log[1 + Exp[x] x (1 + 3 x + x^2)], {x, 0, nmax}], x] Range[0, nmax]!

Formula

E.g.f.: log(1 + exp(x)*x*(1 + 3*x + x^2)).

A007469 Shifts left 2 places under Stirling2 transform.

Original entry on oeis.org

1, 1, 1, 2, 5, 16, 66, 343, 2167, 16193, 140919, 1414947, 16258868, 211935996, 3105828560, 50748310068, 918138961643, 18287966027343, 399145502051200, 9505803743367971, 246064556796896554, 6897674469134480653, 208651954748397405264, 6788671409470892058148
Offset: 1

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Author

Keywords

References

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

Programs

  • Maple
    stirtr:= proc(p)
               proc(n) add(p(k)*Stirling2(n, k), k=0..n) end
             end:
    a:= proc(n) option remember; `if`(n<3, 1, aa(n-2)) end:
    aa:= stirtr(a):
    seq(a(n), n=1..25);  # Alois P. Heinz, Jun 22 2012
  • Mathematica
    stirtr[p_] := Function[{n}, Sum[p[k]*StirlingS2[n, k], {k, 0, n}]]; a[n_] := a[n] = If[n<3, 1, aa[n-2]]; aa = stirtr[a]; Table[a[n], {n, 1, 24}] (* Jean-François Alcover, Jan 09 2013, translated from Alois P. Heinz's Maple program *)

A007553 Logarithmic transform of Fibonacci numbers.

Original entry on oeis.org

1, 1, 1, 1, 7, 5, 85, 335, 1135, 15245, 13475, 717575, 4256825, 29782325, 525045275, 243258625, 56809006625, 415670267875, 5068080417875, 104229929847625, 60861649495625, 20784245979986875, 169274937975443125, 3318579283890780625, 75028912866554839375
Offset: 1

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Author

Keywords

Comments

The coefficients of the e.g.f. log(Sum_{n>=0} Fibonacci(n+1)*x^n/n!) produce the sequence [1,1,-1,-1,7,-5,-85,...], offset 0. - Peter Bala, Jan 19 2011
The series reversion of Sum_{n>=1} Fibonacci(n)*x^n/n is an e.g.f. whose coefficient sequence [1,-1,-1,7,-5,-85,335,1135,...] (offset 1) appears to be a signed version of this sequence. - Peter Bala, Jan 19 2011
E.g.f. A(x), A(x)=x*B(x) satisfies the differential equation B'(x) = 1 + B(x) - B(x)*B(x). - Vladimir Kruchinin, Nov 03 2011

References

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

Programs

  • Maple
    b:= proc(n) option remember; (t-> `if`(n=0, 0, t(n) -add(j*t(n-j)*
          binomial(n, j)*b(j), j=1..n-1)/n))(i->(<<0|1>, <1|1>>^i)[2, 2])
        end:
    a:= n-> abs(b(n)):
    seq(a(n), n=1..30);  # Alois P. Heinz, Mar 06 2018
  • Mathematica
    FullSimplify[Abs[Rest[CoefficientList[Series[-2*x/(1+Sqrt[5]) - Log[5+Sqrt[5]] + Log[2+(3+Sqrt[5])*E^(Sqrt[5]*x)], {x, 0, 15}], x] * Range[0, 15]!]]] (* Vaclav Kotesovec, Jun 24 2014 *)
  • Maxima
    b(n):=if n=0 then 1 else b(n-1)-sum(b(i)*b(n-1-i)*binomial(n-1,i),i,1,n-2);
    a(n):=if n=0 then 0 else abs(b(n-1)); # Vladimir Kruchinin, Nov 03 2011
    
  • Maxima
    b(n):=if n=1 then 1 else sum((n+k-1)!*sum(((-1)^(j)/(k-j)!*sum(((sqrt(5)+1)^(n+j-i-1)*5^((i-j)/2)*stirling1(i,j)*2^(-n-j+i+1)*binomial(n+j-2,i-1))/i!,i,j,n+j-1)),j,1,k),k,1,n-1);
    a(n):=if n=1 then 1 else abs(b(n-1));
    makelist(ratsimp(a(n)),n,1,10); # Vladimir Kruchinin, Nov 17 2012
    
  • Sage
    @CachedFunction
    def c(n,k) :
        if n==k: return 1
        if k<1 or k>n: return 0
        return ((n-k)//2+1)*c(n-1,k-1)-2*k*c(n-1,k+1)
    @CachedFunction
    def A007553(n):
        return abs(add(c(n,k) for k in (0..n)))
    [A007553(n) for n in (0..25)] # Peter Luschny, Jun 10 2014

Formula

b(n) = b(n-1) - Sum_{i=1..n-2} b(i)*b(n-1-i)*binomial(n-1,i), b(0)=1. a(n+1) = abs(b(n)). - Vladimir Kruchinin, Nov 03 2011
Let e.g.f. E(x) = log(1 + Sum_{n>=1} Fibonacci(n+1)*x^n/n!), then g.f. A(x)=x*(1+1/Q(0)), where Q(k) = 1/(x*(k+1)) + 1 + 1/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, May 07 2013
Let F(x) = log(Sum_{n>=0} Fibonacci(n+1)*x^n/n!) be the e.g.f., produce the sequence [1,1,-1,-1,7,-5,-85,...], then g.f. A(x)= 1 + x/Q(0), where Q(k) = 1 + x*(2*k+1) + x^2*(2*k+1)*(2*k+2)/(1 + x*(2*k+2) + x^2*(2*k+2)*(2*k+3)/Q(k+1) ) ; (continued fraction). - Sergei N. Gladkovskii, Sep 23 2013
a(n) ~ 2*(n-1)! * abs(cos(n*arctan(Pi/log(2/(3+sqrt(5)))))) * (5/(Pi^2+log(2/(3+sqrt(5)))^2))^(n/2). - Vaclav Kotesovec, Jun 24 2014

A112005 Logarithmic transform of Fibonacci numbers A000045.

Original entry on oeis.org

0, 1, 0, 1, -2, 4, -17, 82, -384, 2189, -14850, 107404, -845537, 7400482, -70093256, 709888645, -7721333538, 89774204756, -1107347563761, 14456268008050, -199350032354000, 2893615098314941, -44089764970860290, 703841452185590236, -11747695951762870497
Offset: 0

Views

Author

Wolfdieter Lang, Sep 12 2005

Keywords

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; (t-> `if`(n=0, 0, t(n) -add(j*t(n-j)*
          binomial(n, j)*a(j), j=1..n-1)/n))(i->(<<0|1>, <1|1>>^i)[1, 2])
        end:
    seq(a(n), n=0..25);  # Alois P. Heinz, Mar 06 2018
  • Mathematica
    FullSimplify[CoefficientList[Series[Log[1 + 2*E^(x/2)*Sinh[Sqrt[5]*x/2] / Sqrt[5]], {x, 0, 20}], x] * Range[0, 20]!] (* Vaclav Kotesovec, Sep 04 2014 *)

Formula

E.g.f. log(1 + A(x)) with the e.g.f. A(x):=exp(x/2)*sinh(sqrt(5)*x/2)/(sqrt(5)/2) of A000045.
a(n) ~ -(n-1)! / r^n, where r = -1.37807491378452630283968362340785266756... is the root of the equation 2*(5-3*sqrt(5))*r + (sqrt(5)-5) * (log(5/4) + 2*log(1-coth(sqrt(5)*r/2))) = 0. - Vaclav Kotesovec, Sep 04 2014

A279012 Expansion of Product_{k>=1} 1/(1 - x^(k*(5*k-3)/2)).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 9, 10, 11, 11, 11, 12, 12, 13, 14, 15, 15, 15, 16, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25, 26, 26, 27, 28, 29, 31, 32, 33, 33, 34, 35, 37, 39, 41, 42, 43, 45, 46, 48, 50, 52, 53, 54, 56, 58, 60, 62, 64, 65, 67, 69, 72, 75, 78
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 03 2016

Keywords

Comments

Number of partitions of n into nonzero heptagonal numbers (A000566).

Examples

			a(8) = 2 because we have [7, 1] and [1, 1, 1, 1, 1, 1, 1, 1].
		

Crossrefs

Programs

  • Maple
    h:= proc(n) option remember; `if`(n<1, 0, (t->
          `if`(t*(5*t-3)/2>n, t-1, t))(1+h(n-1)))
        end:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          b(n, i-1)+(t-> b(n-t, min(i, h(n-t))))(i*(5*i-3)/2)))
        end:
    a:= n-> b(n, h(n)):
    seq(a(n), n=0..100);  # Alois P. Heinz, Dec 28 2018
  • Mathematica
    nmax=90; CoefficientList[Series[Product[1/(1 - x^(k (5 k - 3)/2)), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - x^(k*(5*k-3)/2)).
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