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 A283243 #16 Mar 06 2017 19:49:41
%S A283243 1,-10,25,53,-270,-77,1057,610,-2031,-5438,-1953,17236,34121,3351,
%T A283243 -103369,-195850,-55471,468448,1067785,764094,-1430780,-4974559,
%U A283243 -6242563,334620,16946199,34459888,29243953,-24503978,-124514921,-205795663,-140256312,191109263
%N A283243 Expansion of exp( Sum_{n>=1} -sigma_2(3*n)*x^n/n ) in powers of x.
%H A283243 Seiichi Manyama, <a href="/A283243/b283243.txt">Table of n, a(n) for n = 0..1000</a>
%F A283243 a(n) = -(1/n)*Sum_{k=1..n} sigma_2(3*k)*a(n-k). - _Seiichi Manyama_, Mar 04 2017
%o A283243 (PARI) A283243_vec(m)=Vec(exp(sum(n=1,m,-sigma(3*n,2)*x^n/n)+x*O(x^m))) \\ Yields m+1 terms a(0..m). - _M. F. Hasler_, Mar 05 2017
%Y A283243 Cf. A283237 (sigma_2(3*n)), A283238 (exp( Sum_{n>=1} sigma_2(3*n)*x^n/n )).
%Y A283243 Cf. exp( Sum_{n>=1} -sigma_k(3*n)*x^n/n ): A185654 (k=1), this sequence (k=2).
%Y A283243 Cf. exp( Sum_{n>=1} -sigma_2(m*n)*x^n/n ): A073592 (m=1), A283242 (m=2), this sequence (m=3).
%K A283243 sign
%O A283243 0,2
%A A283243 _Seiichi Manyama_, Mar 03 2017