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 A081026 #6 Aug 09 2024 08:46:52 %S A081026 1,2,3,5,6,11,12,23,24,47,48,95,96,191,192,383,384,767,768,1535,1536, %T A081026 3071,3072,6143,6144,12287,12288,24575,24576,49151,49152,98303,98304, %U A081026 196607,196608,393215,393216,786431,786432,1572863,1572864,3145727 %N A081026 Variation on Ulam numbers: a(1) = 1; a(2) = 2; for n>2, a(n) = smallest (n odd) or largest (n even) number > a(n-1) that is a unique sum of two distinct earlier terms. %D A081026 Dan Asimov, post to math-fun mailing list, Feb 11, 2003. %F A081026 Appears that a(2k) = 3*2^(k-1)-1, a(2k+1) = 3*2^(k-1) for k >= 1. %Y A081026 Cf. A002858, A081025. %K A081026 nonn %O A081026 1,2 %A A081026 _David W. Wilson_, Mar 02 2003