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 A059904 #4 Oct 14 2022 18:29:30 %S A059904 0,4,33,0,16,516,549755813899,513,0,20,549,548, %T A059904 604462909948052075708555,549764202537,545,0,64,8208, %U A059904 13479973333575319897333507543509815336818572211270286381289293482126 %N A059904 Periodic part of continued fraction for sqrt(n), encoded by recursively interleaving the bits in the binary expansions of the repeating terms. %C A059904 Could be made less gigantic by omitting final terms in continued fraction, which are always 2*c0. %F A059904 a(n) = A059884(A059903(n)). %e A059904 sqrt(3)=1+[1,2] so a(3) is encoded as: %e A059904 .....0 0 0 0 1 -> 1 %e A059904 ....... 1 . 0 .-> 2 %e A059904 -------------- %e A059904 .....000100001 = 33. %Y A059904 A059903, A059884, A003285. %K A059904 base,easy,nonn %O A059904 1,2 %A A059904 _Marc LeBrun_, Feb 07 2001