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 A145831 #3 Jul 14 2012 11:32:21 %S A145831 0,4,0,8,9,8 %N A145831 Log_2 ( A145768( A145830(n))). %o A145831 (PARI) an=0; for( i=1,10^7, an=bitxor(an,i^2); an & an==1<<valuation(an,2) & print1(valuation(an,2)",")) %Y A145831 A145830 = A145768 intersect A000079. A145768(A145830(n)) = 2^a(n). See also A145827-A145829. %K A145831 more,nonn %O A145831 1,2 %A A145831 _M. F. Hasler_, Oct 20 2008