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 A054089 #11 Mar 29 2024 08:47:36 %S A054089 1,3,2,6,4,8,5,11,7,14,9,16,10,19,12,21,13,24,15,27,17,29,18,32,20,35, %T A054089 22,37,23,40,25,42,26,45,28,48,30,50,31,53,33,55,34,58,36,61,38,63,39, %U A054089 66,41,69,43,71,44,74,46,76,47,79,49,82,51 %N A054089 For k >= 1, let p(k) = least h in N not already an a(i), q(k) = p(k)+k, a(2k) = q(k), a(2k+1) = p(k). %Y A054089 Cf. A004957 (even-indexed terms), A026351 (odd-indexed terms). %K A054089 nonn %O A054089 1,2 %A A054089 _Clark Kimberling_