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 A067565 #18 May 02 2017 22:17:16 %S A067565 1,0,0,4,0,2,0,3,9,5,0,6,0,7,8,16,0,10,0,12,14,11,0,15,25,13,18,21,0, %T A067565 20,0,24,22,17,27,36,0,19,26,28,0,30,0,33,32,23,0,35,49,40,34,39,0,48, %U A067565 44,42,38,29,0,45,0,31,50,64,52,55,0,51,46,54 %N A067565 Inverse of R. L. Graham's sequence (A006255), or zero if and only if n is a prime. %C A067565 a(n) = n if and only if n is a perfect square. %C A067565 Also, the greatest m such that there exists a sequence m = a_1 < a_2 < ... < a_t = n such that a_1 * a_2 * ... * a_t is square. - _Peter Kagey_, Dec 27 2016 %H A067565 Peter Kagey, <a href="/A067565/b067565.txt">Table of n, a(n) for n = 1..5000</a> %Y A067565 Cf. A006255. %K A067565 nonn %O A067565 1,4 %A A067565 _Robert G. Wilson v_, Jan 30 2002