This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A015677 #11 Oct 23 2018 07:11:05
%S A015677 1,21,399,6783,102249,1370565,16991415,216411615,3146775345,
%T A015677 49819225365,767467173375,11808542505375,208290421179225,
%U A015677 4084751136190725,76593243172220775,1426967042034909375
%N A015677 Expansion of e.g.f. theta_3^(21/2).
%D A015677 J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 102.
%H A015677 Seiichi Manyama, <a href="/A015677/b015677.txt">Table of n, a(n) for n = 0..445</a>
%t A015677 nmax = 25; CoefficientList[Series[EllipticTheta[3, 0, x]^(21/2), {x, 0, nmax}], x] * Range[0, nmax]! (* _Vaclav Kotesovec_, Oct 23 2018 *)
%K A015677 nonn
%O A015677 0,2
%A A015677 _N. J. A. Sloane_