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 A166506 #5 Jan 04 2013 14:39:27 %S A166506 70,71,72,73,115,116,117,183,185,186,250,251,252,253,365,367,368,427, %T A166506 429,534,535,536,537,594,595,596,640,642,643,645,647,648,649,650,653, %U A166506 654,655,656,657,659,660,661,662,664,665,666,667,669,671,672,673,674 %N A166506 Indices of terms in A166504 which are not in A152242. %F A166506 A166504(a(n)) = A166505(n). %e A166506 a(1)=70 since the first term in A166504 which is not in A152242 is A166504(70)=202. %o A166506 (PARI) c=0; for(i=1,1e4, is_A166504(i) & c++ & !is_A152242(i) & print1(c", ")) %Y A166506 Cf. A152242, A166504, A166505. %K A166506 nonn,base %O A166506 1,1 %A A166506 _M. F. Hasler_, Nov 02 2009