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 A309733 #41 Sep 22 2019 11:55:06 %S A309733 1,1,2,4,7,12,22,36,62,104,174,286,478,780,1284,2100,3433,5586,9114, %T A309733 14798,24064,39050,63376,102726,166584,269835,437190,707964,1146480, %U A309733 1855966,3004748,4863306,7871798,12739576,20617652,33364524,53992834,87369548,141379728,228769842 %N A309733 Expansion of Product_{k>=1} 1/(1 - x^k/(1 - x^(2*k))). %F A309733 a(n) ~ phi^(n+1), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - _Vaclav Kotesovec_, Sep 22 2019 %t A309733 nmax = 40; CoefficientList[Series[Product[1/(1 - x^k/(1 - x^(2*k))), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Sep 22 2019 *) %o A309733 (PARI) N=66; x='x+O('x^N); Vec(1/prod(k=1, N, 1-x^k/(1-x^(2*k)))) %Y A309733 Cf. A006951, A055922, A162891. %K A309733 nonn %O A309733 0,3 %A A309733 _Seiichi Manyama_, Sep 22 2019