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 A173517 #17 Dec 11 2015 12:34:26 %S A173517 0,0,1,2,0,3,4,5,6,0,7,8,9,10,11,12,0,13,14,15,16,17,18,19,20,0,21,22, %T A173517 23,24,25,26,27,28,29,30,0,31,32,33,34,35,36,37,38,39,40,41,42,0,43, %U A173517 44,45,46,47,48,49,50,51,52,53,54,55,56,0,57,58,59,60,61,62,63,64,65,66,67 %N A173517 a(n) = k if n is the k-th nonsquare, zero otherwise. %C A173517 a(A000037(n)) = n; a(A000290(n)) = 0. %C A173517 a(n)*A037213(n) = 0 for all n. %H A173517 Reinhard Zumkeller, <a href="/A173517/b173517.txt">Table of n, a(n) for n = 0..1000</a> %F A173517 a(n) = (1 - A010052(n))*A028391(n). %o A173517 (Haskell) %o A173517 a173517 n = (1 - a010052 n) * a028391 n %o A173517 -- _Reinhard Zumkeller_, Dec 15 2013 %o A173517 (PARI) a(n)=if(issquare(n), 0, n-sqrtint(n)) \\ _Charles R Greathouse IV_, Sep 02 2015 %Y A173517 Cf. A000037, A000196, A000290, A010052, A028391, A037213. %K A173517 nonn,easy %O A173517 0,4 %A A173517 _Reinhard Zumkeller_, Feb 20 2010 %E A173517 Definition revised by _Reinhard Zumkeller_, Dec 15 2013, at the suggestion of _Antti Karttunen_, who further edited the name