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 A293589 #12 Oct 27 2019 18:01:53
%S A293589 1,0,2,-6,12,0,-240,2520,-18480,60480,937440,-21621600,220207680,
%T A293589 -311351040,-34490776320,724669545600,-6625031212800,-49471604582400,
%U A293589 3116728731916800,-58942964451571200,335128094882380800,15732203147781120000,-600651799248659558400
%N A293589 E.g.f.: exp(x^2/(1 + x + x^2)).
%H A293589 Robert Israel, <a href="/A293589/b293589.txt">Table of n, a(n) for n = 0..449</a>
%F A293589 E.g.f.: Product_{k>0} exp(x^(3*k-1)) / exp(x^(3*k)).
%F A293589 (n+3)*(n+2)*(n+1)*n*a(n)+(2*n+1)*(n+3)*(n+2)*a(n+1)+(3*n+4)*(n+3)*a(n+2)+2*(n+3)*a(n+3)+a(n+4)=0. - _Robert Israel_, Oct 27 2019
%p A293589 rec:= (n+3)*(n+2)*(n+1)*n*b(n)+(2*n+1)*(n+3)*(n+2)*b(n+1)+(3*n+4)*(n+3)*b(n+2)+2*(n+3)*b(n+3)+b(n+4)=0:
%p A293589 f:= gfun:-rectoproc({rec,b(0)=1,b(1)=0,b(2)=2,b(3)=-6},b(n),remember):
%p A293589 map(f, [$0..30]); # _Robert Israel_, Oct 27 2019
%t A293589 CoefficientList[Series[E^(x^2/(1 + x + x^2)), {x, 0, 20}], x] * Range[0, 20]! (* _Vaclav Kotesovec_, Oct 13 2017 *)
%o A293589 (PARI) N=66; x='x+O('x^N); Vec(serlaplace(exp(x^2/(1+x+x^2))))
%o A293589 (PARI) N=66; x='x+O('x^N); Vec(serlaplace(prod(k=1, N, exp(x^(3*k-1)-x^(3*k)))))
%Y A293589 Cf. A111884, A293590.
%K A293589 sign
%O A293589 0,3
%A A293589 _Seiichi Manyama_, Oct 12 2017