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.

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A294118 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f.: exp(k*((1+x)^k - 1)).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 4, 1, 0, 1, 9, 20, 1, 0, 1, 16, 99, 112, 1, 0, 1, 25, 304, 1233, 688, 1, 0, 1, 36, 725, 6496, 16929, 4544, 1, 0, 1, 49, 1476, 23425, 152416, 251829, 31936, 1, 0, 1, 64, 2695, 66816, 826225, 3867136, 4012011, 236800, 1, 0, 1, 81, 4544, 162337
Offset: 0

Views

Author

Seiichi Manyama, Oct 23 2017

Keywords

Examples

			Square array A(n,k) begins:
   1, 1,    1,      1,       1, ...
   0, 1,    4,      9,      16, ...
   0, 1,   20,     99,     304, ...
   0, 1,  112,   1233,    6496, ...
   0, 1,  688,  16929,  152416, ...
   0, 1, 4544, 251829, 3867136, ...
		

Crossrefs

Columns k=0..3 give A000007, A000012, A294119, A294120.
Rows n=0..1 give A000012, A000290.
Main diagonal gives A294191.

Formula

A(0,k) = 1 and A(n,k) = k^2 * (n-1)! * Sum_{j=1..min(k,n)} binomial(k-1,j-1)*A(n-j,k)/(n-j)! for n > 0.

A335819 E.g.f.: exp((3/2) * x * (2 + x)).

Original entry on oeis.org

1, 3, 12, 54, 270, 1458, 8424, 51516, 331452, 2230740, 15641424, 113846472, 857706408, 6671592216, 53465326560, 440602852752, 3727748253456, 32332181692464, 287111706003648, 2607272929404000, 24187186030419936, 228997933855499808, 2210786521482955392, 21746223198911853504
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 20 2020

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 23; CoefficientList[Series[Exp[(3/2) x (2 + x)], {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[1] = 3; a[n_] := a[n] = 3 (a[n - 1] + (n - 1) a[n - 2]); Table[a[n], {n, 0, 23}]
  • PARI
    my(x='x+O('x^30)); Vec(serlaplace(exp((3*x*(2 + x)/2)))) \\ Michel Marcus, Nov 21 2020

Formula

G.f.: 1 / (1 - 3*x - 3*x^2 / (1 - 3*x - 6*x^2 / (1 - 3*x - 9*x^2 / (1 - 3*x - 12*x^2 / (1 - ...))))), a continued fraction.
D-finite with recurrence a(n) = 3 * (a(n-1) + (n-1) * a(n-2)).
a(n) = Sum_{k=0..n} binomial(n,k) * A000085(k) * A000898(n-k).
a(n) = Sum_{k=0..n} binomial(n,k) * A202830(k).
a(n) ~ 3^(n/2) * exp(-3/4 + sqrt(3*n) - n/2) * n^(n/2) / sqrt(2). - Vaclav Kotesovec, Aug 09 2021
Showing 1-2 of 2 results.