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

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A161808 G.f.: A(q) = exp( Sum_{n>=1} A162552(n) * 3*A038500(n) * q^n/n ). 1
 1, 3, 3, 3, 9, 12, 12, 27, 36, 57, 141, 165, 135, 321, 450, 399, 780, 1068, 1308, 2913, 3537, 2736, 5940, 8430, 7173, 13251, 18267, 17661, 35007, 45051, 31866, 58506, 85890, 65694, 102000, 145293, 101547, 140574, 203781, 114765, 93051, 161754 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A162552 forms the l.g.f. of log[ Sum_{n>=0} x^(n^2) ], and A038500(n) is the highest power of 3 dividing n. The first negative term is a(43) = -162729. LINKS Paul D. Hanna, Table of n, a(n) for n = 0..10000 (terms 0..100 from Georg Fischer) EXAMPLE G.f.: A(q) = 1 + 3*q + 3*q^2 + 3*q^3 + 9*q^4 + 12*q^5 + 12*q^6 +... log(A(q)) = 3*q - 3*q^2/2 + 9*q^3/3 + 9*q^4/4 - 12*q^5/5 + 45*q^6/6 - 18*q^7/7 +... Compare to: q - q^2/2 + q^3/3 + 3*q^4/4 - 4*q^5/5 + 5*q^6/6 - 6*q^7/7 +... which equals log( Sum_{n>=0} q^(n^2) ) as described by A162552. PROG (PARI) {a(n)=local(Q=sum(m=0, n, x^(m^2))+x*O(x^n), A); A=exp(sum(k=1, n, polcoeff(log(Q), k)*3*3^valuation(k, 3)*x^k)+x*O(x^n)); polcoeff(A, n)} CROSSREFS Cf. A161804 (variant). Sequence in context: A127975 A060828 A332337 * A188344 A217457 A231753 Adjacent sequences:  A161805 A161806 A161807 * A161809 A161810 A161811 KEYWORD sign AUTHOR Paul D. Hanna, Jul 21 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 19 13:08 EST 2021. Contains 340269 sequences. (Running on oeis4.)