A112756 Greatest prime factor of n-th number of the form 3^i*5^j.

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

Offset

1,2

Links

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

Formula

a(n) = A006530(A003593(n));

A112755(n) <= a(n) <= 5.

Mathematica

s = {}; m = 12; Do[n = 5^k; While[n <= 5^m, AppendTo[s, n]; n *= 3], {k, 0, m}]; FactorInteger[#][[-1, 1]] & /@ Union[s]  (* Amiram Eldar, Feb 07 2020 *)

Crossrefs

Cf. A003593, A006530, A086411, A112764, A112755.

Sequence in context: A105439 A142972 A020765 * A121795 A253027 A249384

Adjacent sequences: A112753 A112754 A112755 * A112757 A112758 A112759

Keyword

nonn

Author

Reinhard Zumkeller, Sep 18 2005

Status

approved