The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A087224 G.f. satisfies A(x) = f(x)^2 + x*A(x)*f(x)^3, where f(x) = Sum_{k>=0} x^((4^k-1)/3). 3
 1, 3, 7, 19, 50, 133, 352, 935, 2482, 6584, 17473, 46365, 123034, 326478, 866338, 2298895, 6100296, 16187616, 42955106, 113984740, 302467434, 802621041, 2129817812, 5651638433, 14997065388, 39795888008, 105601506802 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) = A087221(3n+2). EXAMPLE Given f(x) = 1 + x + x^5 + x^21 + x^85 + x^341 + ... so that f(x)^2 = 1 + 2x + x^2 + 2x^5 + 2x^6 + x^10 + 2x^21 + ... and f(x)^3 = 1 + 3x + 3x^2 + x^3 + 3x^5 + 6x^6 + 3x^7 + 3x^10 + ... then A(x) = (1 + 2x + x^2 + 2x^5 + ...) + x*A(x)*(1 + 3x + 3x^2 + x^3 + 3x^5 + ...) = 1 + 3x + 7x^2 + 19x^3 + 50x^4 + 133x^5 + 352x^6 + ... PROG (PARI) a(n)=local(A, m); if(n<1, n==0, m=1; A=1+O(x); while(m<=3*n+3, m*=4; A=1/(1/subst(A, x, x^4)-x)); polcoeff(A, 3*n+2)) CROSSREFS Cf. A087221, A087222, A087223. Sequence in context: A147234 A171854 A182895 * A308398 A341703 A078059 Adjacent sequences:  A087221 A087222 A087223 * A087225 A087226 A087227 KEYWORD nonn AUTHOR Paul D. Hanna, Aug 27 2003 STATUS approved

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

Last modified November 29 13:17 EST 2021. Contains 349416 sequences. (Running on oeis4.)