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 A158263 a(n) = coefficient of x^n in the (2^(n+1))-th iteration of x+x^2 for n>=1. 4
 1, 8, 240, 30256, 15665664, 32668147008, 272033712041216, 9024264001164470016, 1192791193150627685091840, 628748300357129103400036998144, 1322980853407936018020929177243811840 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE Table of coefficients in the (2^i)-th iteration of x+x^2 begins: 1,1; 1,2,2,1; (1),4,12,30,64,118,188,258,302,298,244,162,84,32,8,1; 1,(8),56,364,2240,13188,74760,409836,2179556,11271436,56788112,...; 1,16,(240),3480,49280,685160,9383248,126855288,1695695976,...; 1,32,992,(30256),912640,27297360,810903456,23950328688,...; 1,64,4032,252000,(15665664),969917088,59855127360,3683654668512,...; 1,128,16256,2056384,259445760,(32668147008),4106848523904,...; 1,256,65280,16613760,4222658560,1072200161920,(272033712041216),...; 1,512,261632,133563136,68139438080,34745409189120,17710292513905152,(9024264001164470016),...; ... Where the terms in parenthesis form the initial terms of this sequence. PROG (PARI) {a(n)=local(G=x+x^2+x*O(x^n)); if(n<0, 0, for(i=1, n+1, G=subst(G, x, G+x*O(x^n))); polcoeff(G, n, x))} CROSSREFS Cf. A158260, A158261, A158262, A158264 (table). Sequence in context: A320605 A302005 A301778 * A221417 A351367 A351370 Adjacent sequences: A158260 A158261 A158262 * A158264 A158265 A158266 KEYWORD nonn AUTHOR Paul D. Hanna, Mar 15 2009 STATUS approved

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Last modified March 22 12:59 EDT 2023. Contains 361430 sequences. (Running on oeis4.)