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 A261094 #6 Aug 10 2015 07:33:17 %S A261094 0,1,2,0,3,4,0,5,6,7,0,0,8,9,10,0,11,12,0,0,13,14,15,0,16,17,0,18,19, %T A261094 20,0,0,0,21,22,23,0,24,25,0,26,27,28,0,0,29,30,31,0,32,33,0,0,0,34, %U A261094 35,36,0,37,38,0,39,40,41,0,0,42,43,44,0,45,46,0,0,47,48,49,0,50,51,0,52,53,54,0,0,0,0,55,56,57,0,58,59,0,60,61,62 %N A261094 Left inverse of A219640: If n = A219640(k) for some k, then a(n) = k, otherwise zero. %H A261094 Antti Karttunen, <a href="/A261094/b261094.txt">Table of n, a(n) for n = 0..10946</a> %F A261094 a(n) = A261092(n) * A261093(n). %F A261094 Other identities. For all n >= 0: %F A261094 a(A219640(n)) = n. %o A261094 (Scheme) (define (A261094 n) (* (A261092 n) (A261093 n))) %Y A261094 Cf. A219640, A261092, A261093. %K A261094 nonn %O A261094 0,3 %A A261094 _Antti Karttunen_, Aug 08 2015