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 A175250 #2 Mar 30 2012 19:00:23 %S A175250 1,4,6,9,12,18,21,26,28,34,42,45,52,57,60,65,74,81,84,91,95,98,106, %T A175250 112,119,128,133,135,141,143 %N A175250 Nonprimes (A018252) with noncomposite (A008578) subscripts. %C A175250 a(n) = nonprime(noncomposite(n)) = A018252(A008578(n)). a(n) U A102615(n+1) = A018252(n) for n >= 1. a(1) = 1, a(n) = A078782(n-1) = nonprimes (A008578) with prime (A000040) subscripts for n >=2. %e A175250 a(5) = 12 because a(5) = b(q(5)) = b(7) = 12, q = noncomposite, b = nonprime. %K A175250 nonn %O A175250 1,2 %A A175250 _Jaroslav Krizek_, Mar 13 2010