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 A257681 #8 May 05 2015 14:00:11 %S A257681 0,1,2,3,1,4,5,6,7,8,9,10,2,11,12,13,3,14,1,15,16,17,4,18,19,20,21,22, %T A257681 23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,5,43,44, %U A257681 45,6,46,47,48,49,50,51,52,7,53,54,55,8,56,9,57,58,59,10,60,2 %N A257681 Column index of A257503: If A257685(n) = 0, then a(n) = A257682(n), otherwise a(n) = a(A257685(n)). %C A257681 a(0) = 0 by convention, because 0 is not present in arrays A257503 and A257505. %H A257681 Antti Karttunen, <a href="/A257681/b257681.txt">Table of n, a(n) for n = 0..10080</a> %F A257681 If A257685(n) = 0, then a(n) = A257682(n), otherwise a(n) = a(A257685(n)). %o A257681 (Scheme, two versions, utilizing memoizing definec-macro) %o A257681 (definec (A257681 n) (if (zero? (A257685 n)) (A257682 n) (A257681 (A257685 n)))) %o A257681 (definec (A257681 n) (if (or (zero? n) (= 1 (A257680 n))) (A257682 n) (A257681 (A257685 n)))) %Y A257681 Cf. A257680, A257682, A257685. %Y A257681 Column index of A257503, row index of A257505. %Y A257681 Cf. also A257679 (gives the other index). %K A257681 nonn %O A257681 0,3 %A A257681 _Antti Karttunen_, May 04 2015