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

Offset: 1

Author

Reinhard Zumkeller, Sep 18 2005

Keywords

• nonn

Links

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

Crossrefs

Cf. A051037, A006530, A086411, A112756, A112763.

Programs

Magma

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

Mathematica

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

Formula

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

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