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 A030277 #12 Aug 08 2019 21:06:39 %S A030277 1,1,1,2,4,10,28,86,286,1019,3857,15418,64782,285041,1309355,6263085, %T A030277 31127475,160432093,856039863,4721638083,26883787141,157812750656, %U A030277 953995201996,5932516347277,37913110456751,248768719522450,1674488577654500,11553041105489900 %N A030277 Shifts left 2 places under COMPOSE transform. %H A030277 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a> %F A030277 G.f. A(x) satisfies: A(x) = x + x^2 * (1 + A(A(x))). - _Ilya Gutkovskiy_, May 10 2019 %t A030277 Nest[x + x^2 + x^2 (# /. x -> #) &, O[x], 20][[3]] (* _Vladimir Reshetnikov_, Aug 08 2019 *) %Y A030277 Cf. A030266. %K A030277 nonn,eigen %O A030277 1,4 %A A030277 _Christian G. Bower_