A112764 - OEIS

A112764

Greatest prime factor of the n-th 5-smooth number.

1, 2, 3, 2, 5, 3, 2, 3, 5, 3, 5, 2, 3, 5, 3, 5, 3, 5, 2, 3, 5, 5, 3, 5, 3, 5, 2, 3, 5, 5, 3, 5, 3, 5, 3, 5, 5, 2, 5, 3, 5, 5, 3, 5, 3, 5, 3, 5, 5, 3, 5, 2, 5, 3, 5, 5, 3, 5, 5, 3, 5, 5, 3, 5, 5, 3, 5, 2, 5, 3, 5, 5, 5, 3, 5, 5, 3, 5, 3, 5, 5, 3, 5, 5, 3, 5, 2, 5, 5, 3, 5, 5, 5, 5, 3, 5, 5, 3, 5, 3, 5, 5, 3, 5, 5

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A006530(A051037(n));

A112763(n) <= a(n) <= 5.

MATHEMATICA

Reap[Do[p = FactorInteger[n][[-1, 1]]; If[p < 7, Sow[p]], {n, 1, 2000}] ][[2, 1]] (* Jean-François Alcover, Dec 17 2017 *)

PROG

(Magma) [1] cat [Max(PrimeDivisors(k)): k in [2..1500]| PrimeDivisors(k) subset [2, 3, 5]]; // Marius A. Burtea, Feb 07 2020