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 A023582 #15 Apr 29 2019 11:01:16 %S A023582 1,1,1,1,2,1,2,1,2,2,1,1,1,2,2,3,2,1,2,2,2,1,3,2,1,2,2,2,2,2,2,2,3,1, %T A023582 2,2,1,2,2,3,3,1,2,3,2,1,1,2,2,1,3,2,2,2,2,3,2,1,2,3,2,3,1,2,1,2,1,1, %U A023582 3,2,3,2,1,2,1,3,3,2,2,2,2,1,3,2,1,3,3,2,2,2,2,3,2,2,1,3,2,2,3 %N A023582 Number of distinct prime divisors of 2*prime(n)-1. %H A023582 G. C. Greubel, <a href="/A023582/b023582.txt">Table of n, a(n) for n = 1..5000</a> %F A023582 a(n) = A001221(A076274(n)). - _Michel Marcus_, Oct 01 2013 %p A023582 seq(nops(numtheory:-factorset(2*ithprime(n)-1)),n=1..120); # _Muniru A Asiru_, Apr 29 2019 %t A023582 PrimeNu[2*Prime[Range[100]]-1] (* _Harvey P. Dale_, Jan 25 2015 *) %o A023582 (PARI) a(n) = omega(2*prime(n)-1); \\ _Michel Marcus_, Oct 01 2013 %K A023582 nonn %O A023582 1,5 %A A023582 _Clark Kimberling_