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A093635 G.f.: A(x) = Product_{n>=0} (1+a(n)*x^(n+1))^2 = Sum_{n>=0} a(n)*x^n. 4
1, 2, 5, 18, 64, 258, 1061, 4572, 19809, 88972, 400600, 1844602, 8511540, 39919338, 187389085, 891158688, 4238242129, 20365627200, 97881057229, 474301930632, 2297986873946, 11213069093460, 54697034675149, 268399278895406 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Equals the self-convolution of A093636.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..450

EXAMPLE

( (1+x)(1+2x^2)(1+5x^3)(1+18x^4) )^2 = 1+2x+5x^2+18x^3+...

MAPLE

A:= proc(n) option remember; local i, p, q; if n=0 then 1 else

      p, q:= A(n-1), 1; for i from 0 to n-1 do q:= convert(

        series(q*(1+coeff(p, x, i)*x^(i+1))^2, x, n+1), polynom)

      od: q fi

    end:

a:= n-> coeff(A(n), x, n):

seq(a(n), n=0..30);  # Alois P. Heinz, Aug 01 2013

PROG

(PARI) a(n) =polcoeff(prod(i=0, n-1, (1+a(i)*x^(i+1))^2)+x*O(x^n), n)

CROSSREFS

Cf. A032305, A093636.

Sequence in context: A148428 A266833 A148429 * A024025 A084518 A150014

Adjacent sequences:  A093632 A093633 A093634 * A093636 A093637 A093638

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Apr 07 2004

STATUS

approved

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Last modified October 17 07:57 EDT 2018. Contains 316276 sequences. (Running on oeis4.)