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 A087745 #13 May 03 2023 09:13:34 %S A087745 1,1,3,3,5,5,15,15,17,17,51,51,85,85,255,255,257,257,771,771,1285, %T A087745 1285,3855,3855,4369,4369,13107,13107,21845,21845,65535,65535,65537, %U A087745 65537,196611,196611,327685,327685,983055,983055,1114129,1114129 %N A087745 Numbers A001317 repeated. %C A087745 Triangles A049444, A049459, A051338, A051379, A051523 (Mitrinovic's triangles) mod 2 converted to decimal. %C A087745 Sequence [1, 3, 5, 15, 17, 51, 85, 255, 257, ...] = A001317. %o A087745 (Python) %o A087745 def A087745(n): return sum((bool(~(m:=n>>1)&m-k)^1)<<k for k in range((n>>1)+1)) # _Chai Wah Wu_, May 02 2023 %Y A087745 Cf. A001317, A049444, A049459, A051338, A051378, A051523. %K A087745 easy,nonn %O A087745 0,3 %A A087745 _Philippe Deléham_, Oct 02 2003 %E A087745 Definition corrected and edited by _Omar E. Pol_, Dec 24 2008