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A086412 Number of distinct prime factors of 3-smooth numbers. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,5
LINKS
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
Sequence in context: A078703 A090629 A248623 * A192006 A006928 A087890
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jul 18 2003
STATUS
approved

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Last modified June 14 13:49 EDT 2024. Contains 373400 sequences. (Running on oeis4.)