OFFSET
1,4
COMMENTS
Equivalently, the number of prime divisors, counted with multiplicity, of the largest 5-smooth divisor of n.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
a[n_] := Plus @@ IntegerExponent[n, {2, 3, 5}]; Array[a, 100]
PROG
(PARI) a(n) = valuation(n, 2) + valuation(n, 3) + valuation(n, 5);
(Python)
from sympy import multiplicity as v
def a(n): return v(2, n) + v(3, n) + v(5, n)
print([a(n) for n in range(1, 88)]) # Michael S. Branicky, Jul 25 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Amiram Eldar, Jul 23 2022
STATUS
approved