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 A090080 #3 Mar 30 2012 18:50:42 %S A090080 2,1,5,1,5,5,5,5,5,5,1,21,21,21,5,21,5,5,5,5,21,5,21,21,5,21,5,21,21, %T A090080 5,1,5,21,21,85,21,21,21,21,85,21,85,5,5,21,5,21,5,5,21,21,5,5,5,5,5, %U A090080 21,5,85,21,21,85,21,21,21,21,85,85,85,85,21,21,21,85,21,5,21,21,21 %N A090080 In binary expansion of n-th prime: reduce contiguous blocks of 0's to 0 and contiguous blocks of 1's to 1. %C A090080 a(n) = A090079(A000040(n)). %e A090080 A000040(25)=97 -> '1100001' -> [11][0000][1] -> [1][0][1] -> %e A090080 '101' -> 5=a(25). %Y A090080 Cf. A004676. %K A090080 nonn,base %O A090080 1,1 %A A090080 _Reinhard Zumkeller_, Nov 20 2003