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.

A336713 a(0) = 1 and a(n) = (1/n) * Sum_{k=1..n} (-1)^(n-k) * binomial(n,k) * binomial(n+(n-1)*k,k-1) for n > 0.

Original entry on oeis.org

1, 1, 1, 6, 76, 1447, 37206, 1212194, 47975271, 2238595055, 120453255172, 7347494056729, 501273291296174, 37833413358907566, 3130557361463956074, 281854137496597897755, 27433898122963009937892, 2870816347095046227070383, 321430790732030793454519088
Offset: 0

Views

Author

Seiichi Manyama, Aug 01 2020

Keywords

Crossrefs

Main diagonal of A336708.

Programs

  • Mathematica
    a[0] = 1; a[n_] := Sum[(-1)^(n - k) * Binomial[n, k] * Binomial[n + (n - 1)*k, k - 1], {k, 1, n}] / n; Array[a, 19, 0] (* Amiram Eldar, Aug 01 2020 *)
  • PARI
    {a(n) = if(n==0, 1, sum(k=1, n, (-1)^(n-k)*binomial(n, k)*binomial(n+(n-1)*k, k-1))/n)}

Formula

a(n) ~ exp(n - 1/2 - exp(-1)) * n^(n - 5/2) / sqrt(2*Pi). - Vaclav Kotesovec, Aug 04 2025

A336714 a(0) = 1 and a(n) = (1/n) * Sum_{k=1..n} (-2)^(n-k) * binomial(n,k) * binomial(n+(n-1)*k,k-1) for n > 0.

Original entry on oeis.org

1, 1, 0, 2, 36, 766, 20910, 707472, 28740656, 1367040950, 74645106114, 4606416653654, 317237242964840, 24130334401571972, 2009783477119978508, 181958565624827141256, 17796032244661580019904, 1870078875109869688744870, 210155525478346375059816234, 25151873422906866362758095642
Offset: 0

Views

Author

Seiichi Manyama, Aug 01 2020

Keywords

Crossrefs

Main diagonal of A336709.

Programs

  • Mathematica
    a[0] = 1; a[n_] := Sum[(-2)^(n - k) * Binomial[n, k] * Binomial[n + (n - 1)*k, k - 1], {k, 1, n}] / n; Array[a, 20, 0] (* Amiram Eldar, Aug 01 2020 *)
  • PARI
    {a(n) = if(n==0, 1, sum(k=1, n, (-2)^(n-k)*binomial(n, k)*binomial(n+(n-1)*k, k-1))/n)}

Formula

a(n) ~ exp(n - 1/2 - 2*exp(-1)) * n^(n - 5/2) / sqrt(2*Pi). - Vaclav Kotesovec, Aug 04 2025

A335871 a(0) = 1 and a(n) = (1/n) * Sum_{k=1..n} binomial(n,k) * binomial(n+(n-1)*k,k-1) for n > 0.

Original entry on oeis.org

1, 1, 3, 20, 234, 4159, 101538, 3182454, 122285201, 5575750271, 294529785168, 17697480642005, 1192398100081202, 89053864927236146, 7302988011333915878, 652439391227186881683, 63077327237347821501754, 6561701255914880362990927, 730833849063629052249986940
Offset: 0

Views

Author

Seiichi Manyama, Aug 01 2020

Keywords

Crossrefs

Main diagonal of A336706.

Programs

  • Mathematica
    a[0] = 1; a[n_] := Sum[Binomial[n, k] * Binomial[n + (n - 1)*k, k - 1], {k, 1, n}] / n; Array[a, 19, 0] (* Amiram Eldar, Aug 01 2020 *)
  • PARI
    {a(n) = if(n==0, 1, sum(k=1, n, binomial(n, k)*binomial(n+(n-1)*k, k-1))/n)}

A336707 Square array T(n,k), n>=0, k>=0, read by antidiagonals, where T(0,k) = 1 and T(n,k) = (1/n) * Sum_{j=1..n} 2^(n-j) * binomial(n,j) * binomial(n+(k-1)*j,j-1) for n > 0.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 3, 6, 1, 1, 4, 11, 20, 1, 1, 5, 19, 45, 72, 1, 1, 6, 30, 100, 197, 272, 1, 1, 7, 44, 201, 562, 903, 1064, 1, 1, 8, 61, 364, 1445, 3304, 4279, 4272, 1, 1, 9, 81, 605, 3249, 10900, 20071, 20793, 17504, 1, 1, 10, 104, 940, 6502, 30526, 85128, 124996, 103049, 72896
Offset: 0

Views

Author

Seiichi Manyama, Aug 01 2020

Keywords

Examples

			Square array begins:
    1,   1,    1,     1,     1,     1,      1, ...
    1,   1,    1,     1,     1,     1,      1, ...
    2,   3,    4,     5,     6,     7,      8, ...
    6,  11,   19,    30,    44,    61,     81, ...
   20,  45,  100,   201,   364,   605,    940, ...
   72, 197,  562,  1445,  3249,  6502,  11857, ...
  272, 903, 3304, 10900, 30526, 73723, 158034, ...
		

Crossrefs

Columns k=0-3 give: A071356(n-1), A001003, A007564, A118346.
Main diagonal gives A336712.

Programs

  • Mathematica
    T[0, k_] := 1; T[n_, k_] := Sum[2^(n - j) * Binomial[n, j] * Binomial[n + (k - 1)*j, j - 1], {j, 1, n}] / n; Table[T[k, n - k], {n, 0, 10}, {k, 0, n}] // Flatten (* Amiram Eldar, Aug 01 2020 *)
  • PARI
    {T(n, k) = if(n==0, 1, sum(j=1, n, 2^(n-j)*binomial(n, j)*binomial(n+(k-1)*j, j-1))/n)}
    
  • PARI
    {T(n, k) = local(A=1+x*O(x^n)); for(i=0, n, A=1+x*A^k/(1-2*x*A)); polcoef(A, n)}

Formula

G.f. A_k(x) of column k satisfies A_k(x) = 1 + x * A_k(x)^k / (1 - 2 * x * A_k(x)).
Showing 1-4 of 4 results.