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 A032307 #10 Jul 02 2021 16:43:27 %S A032307 1,1,1,1,2,2,4,6,10,17,29,50,88,156,279,498,909,1639,3010,5495,10152, %T A032307 18674,34745,64312,120197,223850,420057,785683,1480429,2779462, %U A032307 5253203,9899964,18761327,35461501,67383407,127689713 %N A032307 Shifts left 2 places under "EFK" (unordered, size, unlabeled) transform. %H A032307 Andrew Howroyd, <a href="/A032307/b032307.txt">Table of n, a(n) for n = 1..500</a> %F A032307 G.f.: x + x^2 * exp(Sum_{n>=1} Sum_{k>=1} (-1)^(k+1) * a(n)^k * x^(n*k) / k). - _Ilya Gutkovskiy_, Jun 30 2021 %o A032307 (PARI) %o A032307 EFK(p,n)={prod(k=1, n, 1 + polcoef(p,k)*x^k + O(x*x^n))} %o A032307 seq(n)={my(p=O(1));for(i=0, (n-1)\2, p=1+x*EFK(x*p, 2*i)); Vec(p+O(x^n))} \\ _Andrew Howroyd_, Sep 20 2018 %Y A032307 Cf. A032305. %K A032307 nonn %O A032307 1,5 %A A032307 _Christian G. Bower_