A120954 - OEIS

A120954

G.f. A(x) equals series_reversion(x*F(x))/x where F(x) is the g.f. of A120952; a(2*n) = 0 for n>=1.

1, -1, 0, 12, 0, -663, 0, 70992, 0, -11828220, 0, 2788943940, 0, -882129138002, 0, 360987922171968, 0, -185952081073194180, 0, 117927296241009908400, 0, -90382838151345795658647, 0, 82413028950526359510418224, 0, -88207652178334097954952215796, 0

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OFFSET

0,4

LINKS

Table of n, a(n) for n=0..26.

FORMULA

G.f. satisfies: A(x) = 1/F(x*A(x)) and F(x) = 1/A(x*F(x)) where F(x) = g.f. of A120952.

EXAMPLE

A(x) = 1 - x + 12*x^3 - 663*x^5 + 70992*x^7 - 11828220*x^9 +-...

The g.f. of A120952 is:

F(x) = 1 + x + 2*x^2 - 7*x^3 - 58*x^4 + 369*x^5 + 4572*x^6 --++...

PROG

(PARI) {a(n)=local(A=[1, 1]); for(i=1, n, if(#A%2==1, A=concat(A, t); A[ #A]=-subst(Vec(serreverse(x/Ser(A)))[ #A], t, 0)); if(#A%2==0, A=concat(A, t); A[ #A]=subst(Vec(serreverse(x*Ser(A)))[ #A], t, 0))); Vec(serreverse(x*Ser(A)))[n+1]}

CROSSREFS

Cf. A120952, A120953.

Sequence in context: A119530 A012332 A012455 * A265087 A012337 A012339

Adjacent sequences: A120951 A120952 A120953 * A120955 A120956 A120957

KEYWORD

sign

AUTHOR

Paul D. Hanna, Jul 19 2006

STATUS

approved