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 A071854 #8 Mar 30 2012 18:39:03 %S A071854 1,1,0,1,0,1,0,1,1,1,1,1,0,0,1,2,1,2,1,2,2,2,0,1,1,1,1,3,3,2,1,2,3,3, %T A071854 3,3,2,3,2,3,2,3,2,2,3,3,2,3,3,3,3,3,3,4,3,3,3,4,3,4,3,3,3,4,4,5,5,4, %U A071854 4,4,3,4,3,3,4,4,5,5,4,5,5,5,4,4,4,5,5,5,4,4,5,6,5,5,5,6,5,4,5,6,5,6,5,6,6 %N A071854 a(n) = (number of distinct prime factors in C(2n,n)) - pi(n). %H A071854 T. D. Noe, <a href="/A071854/b071854.txt">Table of n, a(n) for n=1..1000</a> %F A071854 a(n) = A067434(n) - A000720(n) %o A071854 (PARI) for(n=1,200,print1(omega(binomial(2*n,n))-sum(i=1,n,isprime(i)),",")) %K A071854 nonn %O A071854 1,16 %A A071854 _Benoit Cloitre_, Jun 09 2002