This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A107945 G.f. A(x) satisfies: A(x) = x*f(A,A^2/x) where f(,) is Ramanujan's theta function; i.e., A(x) = x*Sum_{n=-oo,+oo} A^(n*(n+1)/2)*(A^2/x)^(n*(n-1)/2)). 1
 1, 2, 6, 22, 92, 424, 2100, 10952, 59220, 328454, 1855548, 10630282, 61585456, 360139296, 2123022032, 12603671392, 75291625002, 452279294266, 2730374221784, 16556643025496, 100801159909630, 615936184506514 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A variant of sequence A107902 by Michael Somos. LINKS FORMULA G.f. satisfies: A(x) = x/Sum_{n=-oo, +oo} x^(-n*(n-1)/2)*A(x)^(n*(3*n-1)/2)). G.f.: A(x) = series_reversion(x^2/G107902(x)) where G107902(x) is g.f. of A107902. EXAMPLE A(x) = x + 2*x^2 + 6*x^3 + 22*x^4 + 92*x^5 + 424*x^6 + 2100*x^7 +... PROG (PARI) {a(n)=local(A); if(n<1, 0, A=x+O(x^2); for(k=2, n, A=x*sum(i=-sqrtint(n-1), sqrtint(n+2), x^(-(i^2-i)/2)*A^((3*i^2-i)/2))); polcoeff(A, n))} CROSSREFS Cf. A107902, A107944. Sequence in context: A001181 A130579 A279570 * A279571 A014330 A225294 Adjacent sequences:  A107942 A107943 A107944 * A107946 A107947 A107948 KEYWORD nonn AUTHOR Paul D. Hanna, May 28 2005 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 December 16 03:14 EST 2019. Contains 330013 sequences. (Running on oeis4.)