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 A366580 #18 Jan 06 2024 12:27:20 %S A366580 1,1,2,2,2,2,3,2,3,4,3,3,3,2,4,5,2,4,4,3,3,5,4,2,6,4,4,6,4,4,5,3,2,6, %T A366580 4,4,4,4,4,7,5,3,7,2,5,9,4,4,4,4,6,8,4,3,5,6,6,7,4,3,7,3,5,11,2,4,6,3, %U A366580 5,8,8,6,8,3,5,11,6,5,7,4,5,11,5,5,10,8 %N A366580 Number of distinct prime divisors of 3^n + 1. %H A366580 Max Alekseyev, <a href="/A366580/b366580.txt">Table of n, a(n) for n = 0..691</a> %F A366580 a(n) = omega(3^n+1) = A001221(A034472(n)). %t A366580 PrimeNu[3^Range[0,100]+1] (* _Paolo Xausa_, Oct 14 2023 *) %o A366580 (PARI) for(n = 0, 100, print1(omega(3^n + 1), ", ")) %Y A366580 Cf. A001221, A002592, A034472, A046799, A057935, A057941, A074476, A133801, A274909, A366577, A366578, A366579. %K A366580 nonn %O A366580 0,3 %A A366580 _Sean A. Irvine_, Oct 13 2023