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 A116051 #2 Mar 30 2012 17:40:36 %S A116051 2,3,6,11,13,17,20,33,39,45,47,52,57,58,59,61,63,64,69,81,83,85,86,89, %T A116051 91,98,100,103,110,115,117,123,128,133,134,135,136,141,142,143,144, %U A116051 145,149,150,153,154,156,158,162,164,167,173,179,181,184,185,187,189 %N A116051 n+sigma(n)+sigma(sigma(n)) is a semiprime (A001358). %e A116051 115 + sigma(115) + sigma(sigma(115)) = 662 = 2*331 %Y A116051 Cf. A001358. %K A116051 nonn %O A116051 1,1 %A A116051 _Giovanni Resta_, Feb 13 2006