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 A301334 #7 Mar 19 2018 22:12:59
%S A301334 1,1,4,30,288,3500,51882,908705,18376192,421518897,10815546010,
%T A301334 306954846231,9547629128208,322979502072591,11805623386524688,
%U A301334 463679308850798265,19474458473055138816,870962008703995217038,41324081662873427484240,2073203796753598883831150,109655938011610286565760400
%N A301334 a(n) = [x^n] 1/(1 + n*(1 - theta_2(sqrt(x))/(2*x^(1/8)))), where theta_2() is the Jacobi theta function.
%C A301334 Number of compositions (ordered partitions) of n into triangular numbers of n kinds.
%H A301334 <a href="/index/Com#comp">Index entries for sequences related to compositions</a>
%H A301334 <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a>
%F A301334 a(n) = [x^n] 1/(1 - n*Sum_{k>=1} x^(k*(k+1)/2)).
%F A301334 a(n) ~ n^n * (1 + 1/n - 3/(2*n^2) - 13/(3*n^3) + 181/(24*n^4) + 2251/(120*n^5) - 34949/(720*n^6) - 221539/(2520*n^7) + 13489169/(40320*n^8) + ...). - _Vaclav Kotesovec_, Mar 19 2018
%t A301334 Table[SeriesCoefficient[1/(1 + n (1 - EllipticTheta[2, 0, Sqrt[x]]/(2 x^(1/8)))), {x, 0, n}], {n, 0, 20}]
%t A301334 Table[SeriesCoefficient[1/(1 - n Sum[x^(k (k + 1)/2), {k, 1, n}]), {x, 0, n}], {n, 0, 20}]
%Y A301334 Cf. A000217, A023361, A301335.
%K A301334 nonn
%O A301334 0,3
%A A301334 _Ilya Gutkovskiy_, Mar 18 2018