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 A135975 #33 Sep 26 2024 05:18:31
%S A135975 2,2,3,2,2,3,3,3,2,2,3,3,3,2,2,2,2,2,5,2,2,2,2,5,4,5,2,4,3,4,5,3,2,2,
%T A135975 3,6,2,4,4,6,2,5,3,4,2,2,3,2,3,2,5,3,4,4,3,5,2,3,3,6,5,2,2,5,3,9,4,3,
%U A135975 5,2,8,4,4,3,5,2,4,6,3,4,2,7,3,4,4,2,5,4,5,3,5,4,3,6,4,3,4,3,4,4
%N A135975 Number of prime factors (without multiplicity) in Mersenne composites A065341.
%C A135975 Currently the smallest prime exponent p for which 2^p-1 is incompletely factored is p = 1213. - _Gord Palameta_, Aug 06 2018
%H A135975 Gord Palameta, <a href="/A135975/b135975.txt">Table of n, a(n) for n = 1..183</a>
%H A135975 GIMPS, <a href="https://www.mersenne.org/M1213">Status of M1213</a>
%H A135975 S. S. Wagstaff, Jr., <a href="https://homes.cerias.purdue.edu/~ssw/cun/">Main Tables</a> from the Cunningham Project: cofactor of M1213 is C297.
%F A135975 a(n) = A001221(A065341(n)). - _Michel Marcus_, Aug 07 2018
%t A135975 k = {}; Do[If[ ! PrimeQ[2^Prime[n] - 1], c = FactorInteger[2^Prime[n] - 1]; d = Length[c]; AppendTo[k, d]], {n, 1, 40}]; k
%t A135975 (PrimeNu /@ Select[2^Prime[Range[40]] - 1, ! PrimeQ[#] &]) (* _Jean-François Alcover_, Aug 13 2014 *)
%o A135975 (PARI) forprime(p=1, 1e3, if(!ispseudoprime(2^p-1), print1(omega(2^p-1), ", "))) \\ _Felix Fröhlich_, Aug 12 2014
%Y A135975 Cf. A000225, A001221, A065341, A054723, A134852.
%K A135975 nonn
%O A135975 1,1
%A A135975 _Artur Jasinski_, Dec 09 2007
%E A135975 a(29)-a(46) from _Felix Fröhlich_, Aug 12 2014
%E A135975 a(47)-a(100) from _Gord Palameta_, Aug 07 2018