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 A284694 #5 Apr 02 2017 10:03:10 %S A284694 1,2,3,2,5,2,7,2,2,2,11,2,13,2,3,2,17,2,19,2,3,2,23,2,2,2,3,2,29,2,31, %T A284694 2,3,2,5,2,37,2,3,2,41,2,43,2,2,2,47,2,2,2,3,2,53,2,5,2,3,2,59,2,61,2, %U A284694 2,2,5,2,67,2,3,2,71,2,73,2,2,2,7,2,79,2,2 %N A284694 Least prime number appearing in the prime tower factorization of n (when n > 1); a(1) = 1. %C A284694 See A182318 for the definition of the prime tower factorization of a number. %C A284694 a(n) <= A020639(n) for any n>0. %H A284694 Rémy Sigrist, <a href="/A284694/b284694.txt">Table of n, a(n) for n = 1..10000</a> %F A284694 a(n) = A020639(A279513(n)) for any n>0. %e A284694 9 = 3^2, hence a(9) = min(3, 2) = 2. %Y A284694 Cf. A020639, A182318, A279513, A284695. %K A284694 nonn %O A284694 1,2 %A A284694 _Rémy Sigrist_, Apr 01 2017