The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A158261 a(n) = coefficient of x^n in the (2^(n-1))-th iteration of x+x^2 for n>=1. 5
 1, 2, 12, 364, 49280, 27297360, 59855127360, 515600292989376, 17478262497392546432, 2341170788069821884925696, 1243964516830446590036473921536, 2629751195406987463208250109864126464 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Paul D. Hanna, Table of n, a(n), n = 1..40. 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,(515600292989376),...; 1,256,65280,16613760,4222658560,1072200161920,272033712041216,68973668731925376,(17478262497392546432),...; ... 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, A158262, A158263, A158264 (table). Sequence in context: A006939 A152686 A131690 * A215956 A251182 A266241 Adjacent sequences:  A158258 A158259 A158260 * A158262 A158263 A158264 KEYWORD nonn AUTHOR Paul D. Hanna, Mar 15 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 29 18:25 EDT 2022. Contains 354913 sequences. (Running on oeis4.)