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 A366660 #12 Jan 07 2024 13:32:09 %S A366660 1,2,3,3,3,5,3,5,6,5,5,7,3,6,8,6,6,9,5,7,8,8,4,12,7,6,11,9,7,12,6,7, %T A366660 10,9,8,12,6,8,12,11,6,14,4,12,16,7,8,15,10,12,13,9,6,15,11,14,13,10, %U A366660 5,18,5,10,16,8,9,15,6,13,13,15,7,19,7,10,19,13,11 %N A366660 Number of distinct prime divisors of 9^n - 1. %H A366660 Max Alekseyev, <a href="/A366660/b366660.txt">Table of n, a(n) for n = 1..690</a> %F A366660 a(n) = omega(9^n-1) = A001221(A024101(n)). %F A366660 a(n) = A133801(2*n) = A133801(n) + A366580(n) - 1. - _Max Alekseyev_, Jan 07 2024 %o A366660 (PARI) for(n = 1, 100, print1(omega(9^n - 1), ", ")) %Y A366660 Cf. A024101, A001221, A057952, A366661, A366662, A366663. %Y A366660 Cf. A046800, A133801, A366604, A366611, A366620, A366632, A366651, A102347, A366681, A366707. %K A366660 nonn %O A366660 1,2 %A A366660 _Sean A. Irvine_, Oct 15 2023