A284694 Least prime number appearing in the prime tower factorization of n (when n > 1); a(1) = 1.

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

Offset: 1

Author

Rémy Sigrist, Apr 01 2017

Keywords

• nonn

Comments

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

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

Examples

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

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A020639, A182318, A279513, A284695.

Formula

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