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.

A353993 Expansion of e.g.f. ( Product_{k>0} 1/(1 - k * x^k) )^(1/(1-x)).

Original entry on oeis.org

1, 1, 8, 63, 668, 7850, 115914, 1847286, 34031024, 682177464, 15049816200, 357564279600, 9212847784392, 252552128708568, 7395084613746816, 229412209982127480, 7524339637608261120, 259675490280634374720, 9418707076419411194304, 357606237255136232451264
Offset: 0

Views

Author

Seiichi Manyama, Aug 06 2022

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(1/prod(k=1, N, 1-k*x^k)^(1/(1-x))))
    
  • PARI
    a353992(n) = n!*sum(k=1, n, sumdiv(k, d, (k/d)^d/d));
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=1, i, a353992(j)*binomial(i-1, j-1)*v[i-j+1])); v;

Formula

a(0) = 1; a(n) = Sum_{k=1..n} A353992(k) * binomial(n-1,k-1) * a(n-k).

A356436 a(n) = n! * Sum_{k=1..n} ( Sum_{d|k} d^(k/d) )/k.

Original entry on oeis.org

1, 5, 23, 146, 874, 8124, 62628, 707664, 7860816, 103284000, 1179669600, 24454569600, 324615427200, 5740203974400, 119579523436800, 2688723275212800, 46084905896601600, 1383333631684300800, 26411386476116275200, 868104140064602112000
Offset: 1

Views

Author

Seiichi Manyama, Aug 07 2022

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=1, n, sumdiv(k, d, d^(k/d))/k);
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(-sum(k=1, N, log(1-k*x^k)/k)/(1-x)))

Formula

a(n) = n! * Sum_{k=1..n} A055225(k)/k.
E.g.f.: -(1/(1-x)) * Sum_{k>0} log(1 - k*x^k)/k.
a(n) ~ (n-1)! * 3^((n + 3 - mod(n,3))/3)/2. - Vaclav Kotesovec, Aug 07 2022

A354340 a(n) = n! * Sum_{k=1..n} ( Sum_{d|k} d^(k/d + 1) )/(k * (n-k)!).

Original entry on oeis.org

1, 7, 38, 264, 1629, 16075, 122366, 1414952, 16076913, 213998983, 2112313774, 53581378400, 664573162941, 9967808211387, 239545427723062, 5933102008956848, 79857813309308609, 2677379355344673255, 44453311791217697686, 1743982053518367438616
Offset: 1

Views

Author

Seiichi Manyama, Aug 15 2022

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=1, n, sumdiv(k, d, d^(k/d+1))/(k*(n-k)!));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(-exp(x)*sum(k=1, N, log(1-k*x^k))))

Formula

a(n) = n! * Sum_{k=1..n} A078308(k)/(k * (n-k)!).
E.g.f.: -exp(x) * Sum_{k>0} log(1-k*x^k).
Showing 1-3 of 3 results.