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 A234017 #10 Jun 11 2017 06:44:21 %S A234017 0,0,1,0,0,2,3,0,0,4,0,0,5,6,7,0,0,8,0,0,9,10,0,0,11,0,0,12,13,14,15, %T A234017 0,0,16,0,0,17,18,0,0,19,0,0,20,21,22,0,0,23,0,0,24,25,0,0,26,0,0,27, %U A234017 28,29,30,31,0,0,32,0,0,33,34,0,0,35,0,0,36,37,38 %N A234017 Inverse function for injection A055938. %C A234017 a(0)=0; thereafter if n occurs as a term of A055938, a(n)=its position in A055938, otherwise zero. This works as an "inverse" function for A055938 in a sense that a(A055938(n)) = n for all n. %C A234017 a(n)*A213714(n) = 0 for all n. %H A234017 Antti Karttunen, <a href="/A234017/b234017.txt">Table of n, a(n) for n = 0..8191</a> %H A234017 Indranil Ghosh, <a href="/A234017/a234017.txt">Python program to generate the sequence</a> %F A234017 a(n) = (1-A079559(n)) * A234016(n). %o A234017 (Scheme) (define (A234017 n) (* (- 1 (A079559 n)) (A234016 n))) %Y A234017 Cf. also A079559, A234016, A055938, A213714, A233275, A233277. %K A234017 nonn %O A234017 0,6 %A A234017 _Antti Karttunen_, Dec 18 2013