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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A294839 Expansion of Product_{k>=1} (1 + x^(2*k-1))^(k*(3*k-1)/2)*(1 + x^(2*k))^(k*(3*k+1)/2). 3
 1, 1, 2, 7, 13, 30, 61, 125, 250, 494, 960, 1835, 3487, 6520, 12105, 22239, 40515, 73207, 131315, 233831, 413625, 727100, 1270405, 2207243, 3814155, 6557164, 11217391, 19099932, 32375026, 54640509, 91836697, 153739008, 256379360, 425964293, 705197513, 1163452547, 1913096832, 3135609791 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Weigh transform of the generalized pentagonal numbers (A001318). LINKS M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to arXiv version] M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to Lin. Alg. Applic. version together with omitted figures] N. J. A. Sloane, Transforms Eric Weisstein's World of Mathematics, Pentagonal Number FORMULA G.f.: Product_{k>=1} (1 + x^k)^A001318(k). a(n) ~ exp(Pi*sqrt(2) * 7^(1/4) * n^(3/4) / (3*5^(1/4)) + 9*Zeta(3) * sqrt(5*n/7) / (4*Pi^2) + (7*Pi^6 - 2430*Zeta(3)^2) * (5/7)^(1/4) * n^(1/4) / (336 * sqrt(2) * Pi^5) + 15*Zeta(3)*(3240*Zeta(3)^2 - 7*Pi^6) / (3136*Pi^8)) * 7^(1/8) / (2^(9/4) * 5^(1/8) * n^(5/8)). - Vaclav Kotesovec, Nov 10 2017 MATHEMATICA nmax = 37; CoefficientList[Series[Product[(1 + x^(2 k - 1))^(k (3 k - 1)/2) (1 + x^(2 k))^(k (3 k + 1)/2), {k, 1, nmax}], {x, 0, nmax}], x] a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d Ceiling[d/2] Ceiling[(3 d + 1)/2]/2, {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 37}] CROSSREFS Cf. A001318, A028377, A294102, A294840, A294841. Sequence in context: A215206 A298215 A127396 * A231478 A320680 A079119 Adjacent sequences:  A294836 A294837 A294838 * A294840 A294841 A294842 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Nov 09 2017 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 5 17:28 EST 2021. Contains 349557 sequences. (Running on oeis4.)