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.

A361599 Expansion of e.g.f. exp( x/(1-x)^3 ) / (1-x).

Original entry on oeis.org

1, 2, 11, 88, 881, 10526, 145867, 2294636, 40302593, 780263866, 16483592171, 376901809472, 9265228770481, 243493769839958, 6808261249400171, 201697053847178836, 6308214318127014017, 207622266953125336946, 7170928402389293540683, 259247888385780787392296
Offset: 0

Views

Author

Seiichi Manyama, Mar 17 2023

Keywords

Crossrefs

Column k=3 of A361600.
Cf. A091695.

Programs

  • Mathematica
    Table[n! * Sum[Binomial[n+2*k,3*k]/k!, {k,0,n}], {n,0,20}] (* Vaclav Kotesovec, Mar 17 2023 *)
  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(x/(1-x)^3)/(1-x)))

Formula

a(n) = n! * Sum_{k=0..n} binomial(n+2*k,3*k)/k! = Sum_{k=0..n} (n+2*k)!/(3*k)! * binomial(n,k).
From Vaclav Kotesovec, Mar 17 2023: (Start)
a(n) = 2*(2*n - 1)*a(n-1) - (n-1)*(6*n - 11)*a(n-2) + (n-2)*(n-1)*(4*n - 9)*a(n-3) - (n-3)^2*(n-2)*(n-1)*a(n-4).
a(n) ~ 3^(-1/8) * exp(-1/27 - 3^(-5/4)*n^(1/4)/8 + sqrt(n/3)/2 + 4*3^(-3/4)*n^(3/4) - n) * n^(n + 1/8) / 2 * (1 + (34237/69120)*3^(1/4)/n^(1/4)). (End)

A361598 Expansion of e.g.f. exp( x/(1-x)^2 ) / (1-x).

Original entry on oeis.org

1, 2, 9, 58, 473, 4626, 52537, 677594, 9762993, 155175778, 2693718281, 50657791482, 1025158123849, 22198908725618, 511885585833273, 12517101011344666, 323402336324055137, 8800318580852865474, 251497162228635927433, 7529081846683064675258
Offset: 0

Views

Author

Seiichi Manyama, Mar 17 2023

Keywords

Crossrefs

Column k=2 of A361600.
Cf. A082579.

Programs

  • Mathematica
    Table[n! * Sum[Binomial[n+k,2*k]/k!, {k,0,n}], {n,0,20}] (* Vaclav Kotesovec, Mar 17 2023 *)
  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(x/(1-x)^2)/(1-x)))

Formula

a(n) = n! * Sum_{k=0..n} binomial(n+k,2*k)/k! = Sum_{k=0..n} (n+k)!/(2*k)! * binomial(n,k).
From Vaclav Kotesovec, Mar 17 2023: (Start)
a(n) = (3*n - 1)*a(n-1) - (n-1)*(3*n - 5)*a(n-2) + (n-2)^2*(n-1)*a(n-3).
a(n) ~ 2^(-1/6) * 3^(-1/2) * exp(-1/12 + 3*2^(-2/3)*n^(2/3) - n) * n^(n + 1/6) * (1 + 1/(2^(2/3)*n^(1/3)) + 83/(360*2^(1/3)*n^(2/3))). (End)

A361616 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = n! * Sum_{j=0..n} binomial(n+(k-1)*(j+1),n-j)/j!.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 7, 1, 1, 4, 15, 34, 1, 1, 5, 25, 103, 209, 1, 1, 6, 37, 214, 885, 1546, 1, 1, 7, 51, 373, 2293, 9051, 13327, 1, 1, 8, 67, 586, 4721, 29176, 106843, 130922, 1, 1, 9, 85, 859, 8481, 70981, 427189, 1425495, 1441729, 1
Offset: 0

Views

Author

Seiichi Manyama, Mar 18 2023

Keywords

Examples

			Square array begins:
  1,    1,    1,     1,     1,      1, ...
  1,    2,    3,     4,     5,      6, ...
  1,    7,   15,    25,    37,     51, ...
  1,   34,  103,   214,   373,    586, ...
  1,  209,  885,  2293,  4721,   8481, ...
  1, 1546 ,9051, 29176, 70981, 146046, ...
		

Crossrefs

Columns k=0..3 give A000012, A002720, A343884, A351767.
Main diagonal gives A361617.

Programs

  • PARI
    T(n,k) = n! * sum(j=0, n, binomial(n+(k-1)*(j+1), n-j)/j!);

Formula

E.g.f. of column k: exp( x/(1-x)^k ) / (1-x)^k.
T(n,k) = Sum_{j=0..n} (n+(k-1)*(j+1))!/(k*j+k-1)! * binomial(n,j) for k > 0.

A361607 a(n) = n! * Sum_{k=0..n} binomial(n+(n-1)*k,n*k)/k!.

Original entry on oeis.org

1, 2, 9, 88, 1457, 35226, 1158097, 49554464, 2664907233, 175012404562, 13725980234201, 1263867766626312, 134795551989905809, 16464112185873351338, 2280346417134518709537, 355060682992984062716176
Offset: 0

Views

Author

Seiichi Manyama, Mar 17 2023

Keywords

Crossrefs

Main diagonal of A361600.
Cf. A293013.

Programs

  • Mathematica
    Table[Sum[Binomial[n, k]*(n*k + n - k)!/(n*k)!, {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Mar 17 2023 *)
  • PARI
    a(n) = sum(k=0, n, (n*k+n-k)!/(n*k)!*binomial(n, k));

Formula

a(n) = n! * [x^n] exp( x/(1-x)^n ) / (1-x).
a(n) = Sum_{k=0..n} (n*k+n-k)!/(n*k)! * binomial(n,k).
log(a(n)) ~ n*(2*log(n) - log(log(n)) - 1 - log(2) + (log(log(n)) + log(2) + 1/2)/log(n)). - Vaclav Kotesovec, Mar 17 2023
Showing 1-4 of 4 results.