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.
N=66; x='x+O('x^N); Vec(1/sum(k=0, N, (k+1)^(k+1)*x^k))
[1,-5,13] cat [-27*(-2)^(n-3): n in [3..50]]; // G. C. Greubel, Jan 04 2023
1,-5,13,seq(-27*(-2)^i,i=0..50); # Robert Israel, Dec 20 2017
CoefficientList[Series[1/Sum[(k+1)*(3*k+2)*x^k/2, {k, 0, 30}], {x, 0, 30}], x] (* Vaclav Kotesovec, Dec 20 2017 *)
Join[{1, -5, 13}, Table[(-1)^n * 27 * 2^(n-3), {n, 3, 30}]] (* Vaclav Kotesovec, Dec 20 2017 *)
LinearRecurrence[{-2},{1,-5,13,-27},40] (* Harvey P. Dale, Mar 22 2025 *)
N=66; my(x='x+O('x^N)); Vec(1/sum(k=0, N, (k+1)*(3*k+2)/2*x^k))
first(n) = Vec((1-x)^3/(1+2*x) + O(x^n)) \\ Iain Fox, Dec 20 2017
[1,-5,13]+[-27*(-2)^(n-3) for n in range(3,51)] # G. C. Greubel, Jan 04 2023