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 1-5 of 5 results.

A306347 Expansion of e.g.f. exp((sin(x) + sinh(x))/2).

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 7, 22, 57, 128, 389, 1904, 9329, 38040, 132147, 542648, 3283633, 20997824, 114657097, 536178880, 2784500161, 19876061312, 153326461311, 1034551839872, 6051063485481, 38079448046208, 312420426154893, 2785055242928768, 22141255520251313
Offset: 0

Views

Author

Ilya Gutkovskiy, May 08 2019

Keywords

Comments

Number of partitions of n-set into blocks congruent to 1 mod 4.

Crossrefs

Programs

  • Mathematica
    nmax = 28; CoefficientList[Series[Exp[(Sin[x] + Sinh[x])/2], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = Sum[Boole[MemberQ[{1}, Mod[k, 4]]] Binomial[n - 1, k - 1] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[n], {n, 0, 28}]
  • PARI
    my(N=40, x='x+O('x^N)); Vec(serlaplace(exp((sin(x)+sinh(x))/2))) \\ Seiichi Manyama, Mar 17 2022
    
  • PARI
    a(n) = if(n==0, 1, sum(k=0, (n-1)\4, binomial(n-1, 4*k)*a(n-4*k-1))); \\ Seiichi Manyama, Mar 17 2022

Formula

a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/4)} binomial(n-1,4*k) * a(n-4*k-1). - Seiichi Manyama, Mar 17 2022

A365911 Expansion of e.g.f. 1 / ( 1 - Sum_{k>=0} x^(4*k+3) / (4*k+3)! ).

Original entry on oeis.org

1, 0, 0, 1, 0, 0, 20, 1, 0, 1680, 240, 1, 369600, 102960, 4160, 168168001, 76876800, 7743840, 137225153280, 93117024001, 17091609600, 182510023324320, 172080261401600, 49615854288001, 369403226582016000, 461748751736204400, 191552892427653120
Offset: 0

Views

Author

Seiichi Manyama, Sep 22 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-(sinh(x)-sin(x))/2)))

Formula

a(0) = 1; a(n) = Sum_{k=0..floor((n-3)/4)} binomial(n,4*k+3) * a(n-4*k-3).
E.g.f.: 1 / ( 1 - (sinh(x) - sin(x))/2 ).

A013369 Expansion of e.g.f. exp(sin(x)-sinh(x)).

Original entry on oeis.org

1, 0, 0, -2, 0, 0, 40, -2, 0, -2240, 480, -2, 246400, -137280, 8320, -44844802, 51251200, -10325120, 12197916160, -24831206402, 11394406400, -4636033573760, 15296025241600, -13230894476802, 2348235343872000
Offset: 0

Views

Author

Patrick Demichel (patrick.demichel(AT)hp.com)

Keywords

Examples

			1-2/3!*x^3+40/6!*x^6-2/7!*x^7-2240/9!*x^9...
		

Crossrefs

Programs

  • Mathematica
    With[{nn=30},CoefficientList[Series[Exp[Sin[x]-Sinh[x]],{x,0,nn}],x] Range[ 0,nn]!] (* Harvey P. Dale, May 13 2020 *)
  • PARI
    my(N=40, x='x+O('x^N)); Vec(serlaplace(exp(sin(x)-sinh(x)))) \\ Seiichi Manyama, Mar 17 2022
    
  • PARI
    a(n) = if(n==0, 1, -2*sum(k=0, (n-3)\4, binomial(n-1, 4*k+2)*a(n-4*k-3))); \\ Seiichi Manyama, Mar 17 2022

Formula

a(0) = 1; a(n) = -2 * Sum_{k=0..floor((n-3)/4)} binomial(n-1,4*k+2) * a(n-4*k-3). - Seiichi Manyama, Mar 17 2022

Extensions

Definition clarified by Harvey P. Dale, May 13 2020

A307979 Expansion of e.g.f. exp((cosh(x) - cos(x))/2) (even powers only).

Original entry on oeis.org

1, 1, 3, 16, 133, 1576, 24783, 495496, 12245353, 364768576, 12838252443, 526095538816, 24781014246253, 1326767681420416, 80013978835916583, 5392682199766283776, 403287063337529642833, 33261775377836063850496, 3009257393136250807614003, 297176659119237977183973376
Offset: 0

Views

Author

Ilya Gutkovskiy, May 08 2019

Keywords

Comments

Number of partitions of a 2n-set into blocks congruent to 2 mod 4.

Crossrefs

Programs

  • Mathematica
    nmax = 19; Table[(CoefficientList[Series[Exp[(Cosh[x] - Cos[x])/2], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]
    a[n_] := a[n] = Sum[Boole[MemberQ[{2}, Mod[k, 4]]] Binomial[n - 1, k - 1] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[2 n], {n, 0, 19}]

Formula

a(n) = (2*n)! * [x^(2*n)] exp((cosh(x) - cos(x))/2).

A365893 Expansion of e.g.f. exp( Sum_{k>=0} x^(5*k+3) / (5*k+3)! ).

Original entry on oeis.org

1, 0, 0, 1, 0, 0, 10, 0, 1, 280, 0, 165, 15400, 1, 30030, 1401400, 6995, 6806800, 190590401, 6506835, 1939938000, 36212380820, 4940624150, 687126039601, 9163671323015, 3761116975000, 297754623925175, 2982764271647875, 3067236941769001
Offset: 0

Views

Author

Seiichi Manyama, Sep 22 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(sum(k=0, N\5, x^(5*k+3)/(5*k+3)!))))

Formula

a(0) = 1; a(n) = Sum_{k=0..floor((n-3)/5)} binomial(n-1,5*k+2) * a(n-5*k-3).
Showing 1-5 of 5 results.