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 A366780 #11 Oct 23 2023 05:22:54
%S A366780 0,0,1,1,1,1,2,2,1,1,2,3,2,3,2,3,1,3,4,3,3,2,2,2,3,3,3,5,3,4,5,3,4,3,
%T A366780 5,4,5,3,5,3,2,4,2,4,5,4,4,6,2,5,5,6,3,5,7,5,2,3,5,4,6,5,4,7,3,2,4,4,
%U A366780 3,3,4,5,2,6,6,6,5,3,6,5,4,2,6,3,6,1,7
%N A366780 Number of distinct prime divisors of A000073(n) (tribonacci numbers).
%H A366780 Amiram Eldar, <a href="/A366780/b366780.txt">Table of n, a(n) for n = 2..365</a>
%F A366780 a(n) = A001221(A000073(n)).
%e A366780 a(8)=2 because the 8th tribonacci number 24 = 2^3*3 has 2 distinct prime factors.
%t A366780 PrimeNu[LinearRecurrence[{1, 1, 1}, {1, 1, 2}, 87]] (* _Amiram Eldar_, Oct 23 2023 *)
%Y A366780 Cf. A000073, A001221, A022307, A366781, A366782.
%K A366780 nonn
%O A366780 2,7
%A A366780 _Sean A. Irvine_, Oct 22 2023