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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 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 * A350982 A289992 A357653 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 February 6 17:09 EST 2023. Contains 360110 sequences. (Running on oeis4.)