OFFSET
1,4
COMMENTS
Omega(n) (A001222) is the number of prime factors of n, counted with multiplicity.
Also the number of ways to choose a prime factor, counting multiplicity, of each positive integer from 2 to n.
FORMULA
a(n > 1) = a(n - 1) * A001222(n).
EXAMPLE
We have a(8) = 1 * 1 * 2 * 1 * 2 * 1 * 3 = 12.
MAPLE
a:= proc(n) option remember; `if`(n<2, n,
numtheory[bigomega](n)*a(n-1))
end:
seq(a(n), n=1..40); # Alois P. Heinz, Sep 29 2019
MATHEMATICA
Table[Product[PrimeOmega[k], {k, 2, n}], {n, 30}]
PROG
(PARI) a(n) = prod(k=2, n, bigomega(k)); \\ Michel Marcus, Sep 29 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 28 2019
STATUS
approved