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A229285 G.f.: Sum_{n>=0} x^n / Product_{k=1..2*n-1} (1 - k*x). 2
1, 1, 2, 8, 42, 260, 1860, 15020, 134336, 1313696, 13911528, 158279872, 1922455440, 24794405328, 338037825952, 4853075024192, 73123573392416, 1152965052858560, 18974557508679104, 325181733420301504, 5791431588096653824, 106990656473333558528, 2046805540661737323136 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Compare to o.g.f. of Bell numbers: Sum_{n>=0} x^n / Product_{k=0..n} (1 - k*x).

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..160

EXAMPLE

G.f.: A(x) = 1 + x + 2*x^2 + 8*x^3 + 42*x^4 + 260*x^5 + 1860*x^6 +...

where

A(x) = 1 + x/(1-x) + x^2/((1-x)*(1-2*x)*(1-3*x)) + x^3/((1-x)*(1-2*x)*(1-3*x)*(1-4*x)*(1-5*x)) +...

PROG

(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+sum(m=0, n, x^m/prod(k=1, 2*m-1, 1-k*x+x*O(x^n)))); polcoeff(A, n)}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A229286.

Sequence in context: A130649 A054993 A188912 * A005315 A182520 A121635

Adjacent sequences:  A229282 A229283 A229284 * A229286 A229287 A229288

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Sep 18 2013

STATUS

approved

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Last modified June 21 21:22 EDT 2018. Contains 305642 sequences. (Running on oeis4.)