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 A191868 #9 May 13 2013 01:49:39 %S A191868 1,4,7,13,19,31,37,43,61,67,73,79,97,103,109,127,139,151,157,163,181, %T A191868 193,199,211,223,229,241,271,277,283,307,313,331,337,349,367,373,379, %U A191868 397,409,421,433,439,448,457,463,487,499,523,541 %N A191868 Numbers n such that (product of divisors of 2n) mod (sum of divisors of 2n) is equal to number of divisors of 2n. %o A191868 (PARI) is(n)=my(t=2*n,P=if(issquare(t,&t), t^numdiv(t^2),t^(numdiv(t)/2))); P%sigma(2*n)==numdiv(2*n) \\ _Charles R Greathouse IV_, Jun 19 2011 %Y A191868 Cf. A000005, A000203, A007955, A016777, A187680. %K A191868 nonn,less %O A191868 1,2 %A A191868 _Juri-Stepan Gerasimov_, Jun 18 2011 %E A191868 More terms from _Charles R Greathouse IV_, Jun 19 2011