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 A067390 #14 Sep 08 2022 08:45:05
%S A067390 1,1,1,1,2,1,1,2,2,2,2,1,3,2,1,1,3,1,3,3,3,3,3,2,2,2,2,1,4,1,3,2,4,3,
%T A067390 2,3,3,2,2,2,3,2,4,4,2,2,3,2,3,3,4,2,5,2,1,3,3,3,4,3,2,2,4,2,5,2,1,5,
%U A067390 3,3,3,3,3,4,4,2,4,3,4,5,4,4,5,1,4,4,2,3,5,4,4,4,4,5,4,4,6,3,2,2
%N A067390 Number of distinct prime factors in 2^n + 3.
%H A067390 Amiram Eldar, <a href="/A067390/b067390.txt">Table of n, a(n) for n = 1..699</a>
%F A067390 a(n) = A001221(A062709(n)). - _Amiram Eldar_, Feb 06 2020
%e A067390 a(5) = 2 since 2^5 + 3 = 35 = 5 * 7 has 2 distinct prime factors.
%t A067390 PrimeNu @ Table[2^n + 3, {n, 1, 50}] (* _Amiram Eldar_, Feb 06 2020 *)
%o A067390 (Magma) [#PrimeDivisors(2^n+3):n in [1..100]]; // _Marius A. Burtea_, Feb 06 2020
%Y A067390 Cf. A001221, A062709.
%K A067390 nonn
%O A067390 1,5
%A A067390 _Benoit Cloitre_, Feb 23 2002