A112763 Smallest prime factor of the n-th 5-smooth number.

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

Offset

1,2

Links

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

Formula

a(n) = A020639(A051037(n));

a(n) <= A112764(n) <= 5.

a(A188427(n)) = 5 for n > 1. - David A. Corneth, Feb 07 2020

Mathematica

FactorInteger[#][[1, 1]] & /@ Select[Range[3000], Last @ Map[First, FactorInteger[#]] <= 5 &] (* Amiram Eldar, Feb 07 2020 *)

Prog

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

Crossrefs

Cf. A020639, A051037, A086410, A112755, A112764, A188425, A188426, A188427.

Sequence in context: A127705 A124386 A098668 * A093476 A262597 A217607

Adjacent sequences: A112760 A112761 A112762 * A112764 A112765 A112766

Keyword

nonn

Author

Reinhard Zumkeller, Sep 18 2005

Status

approved