A284694 - OEIS

%I #5 Apr 02 2017 10:03:10

%S 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 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 2,2,5,2,67,2,3,2,71,2,73,2,2,2,7,2,79,2,2

%N Least prime number appearing in the prime tower factorization of n (when n > 1); a(1) = 1.

%C See A182318 for the definition of the prime tower factorization of a number.

%C a(n) <= A020639(n) for any n>0.

%H Rémy Sigrist, <a href="/A284694/b284694.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A020639(A279513(n)) for any n>0.

%e 9 = 3^2, hence a(9) = min(3, 2) = 2.

%Y Cf. A020639, A182318, A279513, A284695.

%K nonn

%O 1,2

%A _Rémy Sigrist_, Apr 01 2017