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 A120017 The 2nd self-composition of A120010; g.f.: A(x) = G(G(x)), where G(x) = g.f. of A120010. 2
 1, 2, 4, 10, 32, 116, 440, 1708, 6760, 27232, 111392, 461536, 1933024, 8170400, 34807232, 149304080, 644298592, 2795216576, 12184415360, 53338632256, 234393350912, 1033614750080, 4572427361536, 20285780245120, 90238113332992 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA G.f.: A(x) = (1 - sqrt(1 - 4*x*(1-x)/(1-2*x+2*x^2) ))/2. EXAMPLE A(x) = x + 2*x^2 + 4*x^3 + 10*x^4 + 32*x^5 + 116*x^6 + 440*x^7 +... G(x) = x + x^2 + x^3 + 2*x^4 + 6*x^5 + 18*x^6 + 53*x^7 + 158*x^8 +... where G(x) is the g.f. of A120010 and G(G(x)) = A(x). PROG (PARI) {a(n)=polcoeff((1 - sqrt(1 - 4*x*(1-x)/(1-2*x+2*x^2+x*O(x^n)) ))/2, n)} CROSSREFS Cf. A120010, A120018 (3rd self-composition). Sequence in context: A263662 A151400 A071954 * A000736 A263663 A176006 Adjacent sequences:  A120014 A120015 A120016 * A120018 A120019 A120020 KEYWORD nonn AUTHOR Paul D. Hanna, Jun 14 2006 STATUS approved

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Last modified October 23 22:04 EDT 2018. Contains 316541 sequences. (Running on oeis4.)