OFFSET
1,1
COMMENTS
First differs from A185359 at n = 22.
The asymptotic density of terms with least prime factor prime(n) (within all the positive integers) is d(n) = (1/prime(n)^(prime(n)+1)) * Product_{k=1..(n-1)} (1-1/prime(k)). For example, for n = 1, 2, 3, 4 and 5, d(n) = 1/8, 1/162, 1/46875, 4/86472015 and 8/109844993185235.
The asymptotic density of this sequence is Sum_{n>=1} d(n) = 0.13119421909731920416... .
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
8 = 2^3 is a term since its least prime factor, 2, is smaller than its exponent, 3.
MATHEMATICA
q[n_] := Less @@ FactorInteger[n][[1]]; Select[Range[2, 420], q]
PROG
(PARI) is(n) = {my(f = factor(n)); n > 1 && f[1, 1] < f[1, 2]; }
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Amiram Eldar, Sep 22 2023
STATUS
approved