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 1-3 of 3 results.

A354326 Expansion of e.g.f. 1/(1 - x/8 * (exp(4 * x) - 1)).

Original entry on oeis.org

1, 0, 1, 6, 38, 280, 2538, 27524, 341912, 4754880, 73322360, 1244282512, 23048700912, 462565343552, 9996300546512, 231444311970720, 5715911385442688, 149988948332148736, 4167328800543910272, 122218355207805620480, 3773036019063284645120
Offset: 0

Views

Author

Seiichi Manyama, May 24 2022

Keywords

Crossrefs

Programs

  • Mathematica
    With[{nn=20},CoefficientList[Series[1/(1-x/8 (Exp[4x]-1)),{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Oct 03 2023 *)
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x/8*(exp(4*x)-1))))
    
  • PARI
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=2, i, j*4^(j-2)*binomial(i, j)*v[i-j+1])/2); v;
    
  • PARI
    a(n) = n!*sum(k=0, n\2, 4^(n-2*k)*k!*stirling(n-k, k, 2)/(2^k*(n-k)!));

Formula

a(0) = 1; a(n) = (1/2) * Sum_{k=2..n} k * 4^(k-2) * binomial(n,k) * a(n-k).
a(n) = n! * Sum_{k=0..floor(n/2)} 4^(n-2*k) * k! * Stirling2(n-k,k)/(2^k * (n-k)!).

A354327 Expansion of e.g.f. 1/(1 + x/4 * log(1 - 2 * x)).

Original entry on oeis.org

1, 0, 1, 3, 22, 180, 1902, 23730, 344872, 5706288, 105960600, 2181449160, 49311653616, 1214109056160, 32339248301808, 926527371653520, 28410493609687680, 928335829570087680, 32201658919855225728, 1181755749910942408320, 45744743939940787150080
Offset: 0

Views

Author

Seiichi Manyama, May 24 2022

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x/4*log(1-2*x))))
    
  • PARI
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=i!*sum(j=2, i, 2^(j-3)/(j-1)*v[i-j+1]/(i-j)!)); v;
    
  • PARI
    a(n) = n!*sum(k=0, n\2, 2^(n-3*k)*k!*abs(stirling(n-k, k, 1))/(n-k)!);

Formula

a(0) = 1; a(n) = n! * Sum_{k=2..n} 2^(k-3)/(k-1) * a(n-k)/(n-k)!.
a(n) = n! * Sum_{k=0..floor(n/2)} 2^(n-3*k) * k! * |Stirling1(n-k,k)|/(n-k)!.

A354323 Expansion of e.g.f. exp( x/4 * (exp(2 * x) - 1) ).

Original entry on oeis.org

1, 0, 1, 3, 11, 50, 273, 1687, 11505, 86004, 700445, 6163751, 58148547, 584622766, 6235669629, 70286727435, 834288853217, 10395375065096, 135592878107673, 1846897191981835, 26212412703559515, 386874121137659274, 5927186655133112105, 94108950154465139807
Offset: 0

Views

Author

Seiichi Manyama, May 24 2022

Keywords

Crossrefs

Cf. A354325.

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x/4*(exp(2*x)-1))))
    
  • PARI
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=2, i, j*2^(j-3)*binomial(i-1, j-1)*v[i-j+1])); v;
    
  • PARI
    a(n) = n!*sum(k=0, n\2, 2^(n-3*k)*stirling(n-k, k, 2)/(n-k)!);

Formula

a(0) = 1; a(n) = Sum_{k=2..n} k * 2^(k-3) * binomial(n-1,k-1) * a(n-k).
a(n) = n! * Sum_{k=0..floor(n/2)} 2^(n-3*k) * Stirling2(n-k,k)/(n-k)!.
Showing 1-3 of 3 results.