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 A046799 #52 Mar 15 2025 13:51:43 %S A046799 1,1,1,1,1,2,2,2,1,2,2,2,2,2,3,3,1,2,4,2,2,3,3,2,3,4,4,3,2,3,5,2,2,4, %T A046799 4,5,4,3,4,3,2,3,6,2,3,5,5,3,3,3,5,5,3,3,6,5,3,4,3,4,4,2,5,5,2,6,6,3, %U A046799 3,4,6,3,5,3,5,6,4,6,9,2,3,6,5,6,5,4,5,4,4,4,10,6,2,4,4,5,3,5,6,7,6,2,9,3,2 %N A046799 Number of distinct prime factors of 2^n+1. %C A046799 The length of row n in A060444. %H A046799 Max Alekseyev, <a href="/A046799/b046799.txt">Table of n, a(n) for n = 0..1128</a> (terms 0..500 from T. D. Noe; terms 501..1062 from Amiram Eldar) %F A046799 a(n) = A001221(A000051(n)). - _Amiram Eldar_, Oct 04 2019 %e A046799 For n=7, 129 = 3.43 has 2 prime factors, so a(7) = 2. %t A046799 PrimeNu[1 + 2^#] & /@ Range[0, 104] (* _Jayanta Basu_, Jun 29 2013 *) %o A046799 (PARI) a(n) = omega(2^n+1); \\ _Michel Marcus_, Mar 25 2017 %Y A046799 Cf. A000051, A001221, A060444, A086257 (number of primitive prime factors). %K A046799 nonn %O A046799 0,6 %A A046799 _Labos Elemer_