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 A123722 #3 Mar 30 2012 17:37:54 %S A123722 1,3,4,8,9,15,21,33,35,39,51,57,69,70,87,93,111,123,129,141,159,177, %T A123722 183,201,213,219,237,249,267,291,303,309,321,327,339,381,393,411,417, %U A123722 447,453,471,489,501,519,537,543,573,579,591,597,633,669,681,687,699,717 %N A123722 Values of n for which A000224(n)=Ceiling[(n+1)/3]; A000224(n) is the number of squares mod n. %C A123722 Conjecture. If n>2 and a(n) is a multiple of 3, then a(n)/3 is a prime; further, all odd primes are given as a(n)/3 for some n. (This has been verified up to n=2000.) %Y A123722 Cf. A000224, A123723. %K A123722 nonn %O A123722 1,2 %A A123722 _John W. Layman_, Oct 09 2006