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A215117 G.f. A(x) satisfies: A(A(A(A(x)))) = G(x) where G(x) = x + 3*x^2 + x*G(G(G(G(x)))) is the g.f. of A215116. 4
1, 1, 1, 49, 721, 17281, 452065, 13511953, 443435185, 15816390241, 606861668161, 24867738772849, 1082158542264721, 49785517156216897, 2412544311495241633, 122762020478952148177, 6542028190536528941425, 364254737003651267997985, 21146448814786605196994305 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..19.

FORMULA

a(n) == 1 (mod 48).

EXAMPLE

G.f.: A(x) = x + x^2 + x^3 + 49*x^4 + 721*x^5 + 17281*x^6 + 452065*x^7 +...

Let G(x) = A(A(A(A(x)))):

G(x) = x + 4*x^2 + 16*x^3 + 256*x^4 + 4864*x^5 + 111616*x^6 + 2983936*x^7 +...

such that G(x) = x + 3*x^2 + x*G(G(G(G(x)))):

G(G(G(G(x)))) = x + 16*x^2 + 256*x^3 + 4864*x^4 + 111616*x^5 + 2983936*x^6 +...

PROG

(PARI) {a(n)=local(A=x+x^2, B=x+4*x^2); for(i=1, n+1, B=x+3*x^2+x*subst(B, x, subst(B, x, subst(B, x, B+x^2*O(x^n)))));

for(j=1, n+1, A=round((3*A+subst(B, x, serreverse(subst(A, x, subst(A, x, A+x^2*O(x^n))))))/4));; polcoeff(A, n)}

for(n=1, 31, print1(a(n), ", "))

CROSSREFS

Cf. A215116, A213009, A215115, A215119.

Sequence in context: A166832 A299711 A175775 * A289992 A278284 A110906

Adjacent sequences:  A215114 A215115 A215116 * A215118 A215119 A215120

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Aug 03 2012

STATUS

approved

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Last modified May 25 11:17 EDT 2019. Contains 323539 sequences. (Running on oeis4.)