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 1-4 of 4 results.

A354518 Expansion of e.g.f. cosh(x)^exp(x).

Original entry on oeis.org

1, 0, 1, 3, 7, 30, 166, 798, 4117, 27660, 196756, 1328448, 9866407, 86205210, 759842266, 6460661028, 60841732777, 651349676280, 6795873687496, 67981177154688, 770224145659627, 9854500496860470, 116983085896035646, 1301594922821009028, 17440543467561038557
Offset: 0

Views

Author

Seiichi Manyama, Aug 16 2022

Keywords

Comments

a(39) is negative. - Vaclav Kotesovec, Aug 17 2022

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(cosh(x)^exp(x)))
    
  • PARI
    a354520(n) = sum(k=1, n\2, (16^k-4^k)*bernfrac(2*k)/(2*k)*binomial(n, 2*k));
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=1, i, a354520(j)*binomial(i-1, j-1)*v[i-j+1])); v;

Formula

a(0) = 1; a(n) = Sum_{k=1..n} A354520(k) * binomial(n-1,k-1) * a(n-k).

A215515 2n-th derivative of cos(x)^cos(x) at x=0.

Original entry on oeis.org

1, -1, 7, -76, 1597, -41776, 1673167, -74527636, 4832747017, -305644428256, 30618856073947, -2276081971574236, 390042814538656957, -20435946140834126176, 10544180964356207226247, 604793906292405974180324, 688972694565220644332739217
Offset: 0

Views

Author

Michel Lagneau, Aug 14 2012

Keywords

Crossrefs

Programs

  • Maple
    a:= n-> coeff(series(cos(x)^cos(x), x, 2*n+1), x, 2*n)*(2*n)!:
    seq(a(n), n=0..21);  # Alois P. Heinz, Apr 17 2023
  • Mathematica
    f[x_] := Cos[x]^Cos[x]; Table[Derivative[2*n][f][0],{n,0,30}]
  • PARI
    a354520(n) = sum(k=1, n\2, (16^k-4^k)*bernfrac(2*k)/(2*k)*binomial(n, 2*k));
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=1, i, (-1)^j*a354520(2*j)*binomial(2*i-1, 2*j-1)*v[i-j+1])); v; \\ Seiichi Manyama, Aug 17 2022

Formula

a(0) = 1; a(n) = Sum_{k=1..n} (-1)^k * A354520(2*k) * binomial(2*n-1,2*k-1) * a(n-k). - Seiichi Manyama, Aug 17 2022

A215518 2n-th derivative of cosh(x)^cosh(x) at x=0.

Original entry on oeis.org

1, 1, 7, 76, 1597, 41776, 1673167, 74527636, 4832747017, 305644428256, 30618856073947, 2276081971574236, 390042814538656957, 20435946140834126176, 10544180964356207226247, -604793906292405974180324, 688972694565220644332739217, -181007844268190205159712489664
Offset: 0

Views

Author

Michel Lagneau, Aug 14 2012

Keywords

Crossrefs

Programs

  • Maple
    a:= n-> coeff(series(cosh(x)^cosh(x), x, 2*n+1), x, 2*n)*(2*n)!:
    seq(a(n), n=0..21);  # Alois P. Heinz, Aug 15 2012, revised, Apr 14 2023
  • Mathematica
    f[x_] := Cosh[x]^Cosh[x]; Table[Derivative[2*n][f][0],{n,0,30}]
  • PARI
    a354520(n) = sum(k=1, n\2, (16^k-4^k)*bernfrac(2*k)/(2*k)*binomial(n, 2*k));
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=1, i, a354520(2*j)*binomial(2*i-1, 2*j-1)*v[i-j+1])); v; \\ Seiichi Manyama, Aug 17 2022

Formula

From Seiichi Manyama, Aug 17 2022: (Start)
a(0) = 1; a(n) = Sum_{k=1..n} A354520(2*k) * binomial(2*n-1,2*k-1) * a(n-k).
a(n) = (-1)^n * A215515(n). (End)

A354519 Expansion of e.g.f. exp(x) * log(sec(x)).

Original entry on oeis.org

0, 1, 3, 8, 20, 61, 203, 888, 4080, 24001, 140283, 1028048, 7248020, 63374221, 522164243, 5299033488, 49924707840, 576514338721, 6110861416083, 79100066353208, 931434877343540, 13355627237749501, 172948115797623803, 2720827878727067208, 38424408320191299120
Offset: 1

Views

Author

Seiichi Manyama, Aug 16 2022

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); concat(0, Vec(serlaplace(exp(x)*log(1/cos(x)))))
    
  • PARI
    a(n) = sum(k=1, n\2, ((-4)^k-(-16)^k)*bernfrac(2*k)/(2*k)*binomial(n, 2*k));
    
  • Python
    from math import comb
    from sympy import bernoulli
    def A354519(n): return sum(abs(((2-(2<<(m:=k<<1)))*bernoulli(m)<>1)+1)) # Chai Wah Wu, Apr 15 2023

Formula

a(n) = Sum_{k=1..floor(n/2)} A000182(k) * binomial(n,2*k).
a(n) ~ 2^(n + 1/2) * (exp(Pi/2) + (-1)^n/exp(Pi/2)) * n^(n - 1/2) / (Pi^(n - 1/2) * exp(n)). - Vaclav Kotesovec, Aug 17 2022
Showing 1-4 of 4 results.