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.

A354550 Expansion of e.g.f. exp( x * exp(x^2/2) ).

Original entry on oeis.org

1, 1, 1, 4, 13, 46, 241, 1156, 6889, 44668, 300241, 2328976, 18390901, 159273544, 1461200833, 13995753136, 144068872081, 1531949061136, 17259159775969, 202543867724608, 2474236899786781, 31633380519660256, 417760492214548561, 5751414293905728064
Offset: 0

Views

Author

Seiichi Manyama, Aug 18 2022

Keywords

Crossrefs

Programs

  • Mathematica
    With[{nn=30},CoefficientList[Series[Exp[x Exp[x^2/2]],{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Mar 03 2024 *)
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x*(exp(x^2/2)))))
    
  • PARI
    a(n) = n!*sum(k=0, n\2, (n-2*k)^k/(2^k*k!*(n-2*k)!));

Formula

a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/(2^k * k! * (n - 2*k)!).

A354552 Expansion of e.g.f. exp( x * exp(x^4/24) ).

Original entry on oeis.org

1, 1, 1, 1, 1, 6, 31, 106, 281, 946, 7561, 54286, 281161, 1207636, 7997991, 81996916, 701522641, 4580581916, 29742355441, 306369616636, 3632198902321, 34710574441096, 276645112305871, 2652825718776696, 35647605796451881, 458142859493786776
Offset: 0

Views

Author

Seiichi Manyama, Aug 18 2022

Keywords

Comments

This sequence is different from A143568.

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x*(exp(x^4/24)))))
    
  • PARI
    a(n) = n!*sum(k=0, n\4, (n-4*k)^k/(24^k*k!*(n-4*k)!));

Formula

a(n) = n! * Sum_{k=0..floor(n/4)} (n - 4*k)^k/(24^k * k! * (n - 4*k)!).

A356328 a(n) = n! * Sum_{k=0..floor(n/3)} (n - 3*k)^k/(6^k * (n - 3*k)!).

Original entry on oeis.org

1, 1, 1, 1, 5, 21, 61, 281, 2521, 15625, 84841, 971521, 10646461, 83366141, 962405445, 15445935961, 181502928881, 2182235585041, 42297481449361, 714940186390465, 10007476059187381, 204722588272279141, 4600003555996715021, 80767827313930590681
Offset: 0

Views

Author

Seiichi Manyama, Aug 18 2022

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := n! * Sum[(n - 3*k)^k/(6^k*(n - 3*k)!), {k, 0, Floor[n/3]}]; a[0] = 1; Array[a, 24, 0] (* Amiram Eldar, Aug 19 2022 *)
  • PARI
    a(n) = n!*sum(k=0, n\3, (n-3*k)^k/(6^k*(n-3*k)!));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, x^k/(k!*(1-k*x^3/6)))))

Formula

E.g.f.: Sum_{k>=0} x^k / (k! * (1 - k*x^3/6)).

A358265 Expansion of e.g.f. 1/(1 - x * exp(x^3/6)).

Original entry on oeis.org

1, 1, 2, 6, 28, 160, 1080, 8470, 76160, 771120, 8671600, 107245600, 1446984000, 21150929800, 332950217600, 5615507898000, 101024594070400, 1931055071545600, 39082823446867200, 834945681049480000, 18776164188349568000, 443348081412556320000
Offset: 0

Views

Author

Seiichi Manyama, Nov 06 2022

Keywords

Crossrefs

Programs

  • Maple
    g := 1/(1-x*exp(x^3/6)) ;
    taylor(%,x=0,70) ;
    L := gfun[seriestolist](%) ;
    seq( op(i,L)*(i-1)!,i=1..nops(L)) ; # R. J. Mathar, Mar 13 2023
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x*exp(x^3/6))))
    
  • PARI
    a(n) = n!*sum(k=0, n\3, (n-3*k)^k/(6^k*k!));

Formula

a(n) = n! * Sum_{k=0..floor(n/3)} (n - 3*k)^k/(6^k * k!).
a(n) ~ n! / ((1 + LambertW(1/2)) * (2*LambertW(1/2))^(n/3)). - Vaclav Kotesovec, Nov 13 2022

A362661 E.g.f. satisfies A(x) = exp( x * exp(x^3/6) * A(x) ).

Original entry on oeis.org

1, 1, 3, 16, 129, 1356, 17767, 279714, 5149209, 108591688, 2582351451, 68380940904, 1995777685717, 63659665732716, 2203395556479951, 82253291389678756, 3294326092613575473, 140911264444599281616, 6411278790217738946899
Offset: 0

Views

Author

Seiichi Manyama, Apr 29 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(-lambertw(-x*exp(x^3/6)))))

Formula

E.g.f.: exp( -LambertW(-x * exp(x^3/6)) ).
a(n) = n! * Sum_{k=0..floor(n/3)} (n-3*k)^k * (n-3*k+1)^(n-3*k-1) / (6^k * k! * (n-3*k)!).
Showing 1-5 of 5 results.