A086412 Number of distinct prime factors of 3-smooth numbers.

0, 1, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 2, 2, 1, 2, 1, 2, 2, 1, 2, 2, 2, 2, 1, 1, 2, 2, 2, 2, 2, 1, 2, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2

Offset

1,5

Links

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

Formula

a(n) = A001221(A003586(n));

a(n) <= 2.

Mathematica

s = {}; m = 12; Do[n = 3^k; While[n <= 3^m, AppendTo[s, n]; n*=2], {k, 0, m}]; PrimeNu /@ Union[s] (* Amiram Eldar, Jan 29 2020 *)

Crossrefs

Cf. A001221, A003586, A069352, A086414.

Sequence in context: A078703 A090629 A248623 * A192006 A378285 A006928

Adjacent sequences: A086409 A086410 A086411 * A086413 A086414 A086415

Keyword

nonn

Author

Reinhard Zumkeller, Jul 18 2003

Status

approved