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 A308031 #6 May 10 2019 06:51:47 %S A308031 1,1,1,1,1,2,4,8,16,34,78,195,523,1472,4284,12832,39608,126406,418276, %T A308031 1436230,5110170,18785417,71109917,276404921,1101234823,4493335194, %U A308031 18773200580,80320474041,351906635253,1578344960050,7241981076424,33961826526634,162615016927284 %N A308031 G.f. A(x) satisfies: A(x) = x + x^2 + x^3 + x^4 * (1 + A(A(x))). %C A308031 Shifts left 4 places under COMPOSE transform. %t A308031 terms = 33; A[_] = 0; Do[A[x_] = x + x^2 + x^3 + x^4 (1 + A[A[x]]) + O[x]^(terms + 1) // Normal, terms + 1]; Rest[CoefficientList[A[x], x]] %Y A308031 Cf. A030266, A030277, A308030, A308032. %K A308031 nonn %O A308031 1,6 %A A308031 _Ilya Gutkovskiy_, May 10 2019