A258571 Smallest prime factors of 6-full numbers, a(1)=1.

1, 2, 2, 2, 2, 3, 2, 2, 3, 2, 3, 2, 5, 2, 3, 2, 2, 3, 2, 5, 2, 7, 2, 2, 3, 2, 2, 2, 2, 5, 2, 2, 3, 2, 2, 7, 2, 2, 2, 2, 2, 2, 3, 2, 11, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 13, 2, 2, 7, 2, 2, 2, 2, 2, 2, 2, 5, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 11, 2, 2, 2

Offset: 1

Author

Reinhard Zumkeller, Jun 06 2015

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..10000 (terms 1..191 from Reinhard Zumkeller)

Crossrefs

Cf. A069493, A020639, A258603, A258567, A258568, A258569, A258570.

Programs

Haskell

a258571 = a020639 . a069493

PARI

lista(kmax) = {my(f); print1(1, ", "); for(k = 2, kmax, f = factor(k); if(vecmin(f[, 2]) > 5, print1(f[1, 1], ", "))); } \\ Amiram Eldar, Sep 12 2024

Formula

a(n) = A020639(A069493(n)).

a(A258603(n)) = A000040(n) and a(m) != A000040(n) for m < A258603(n).