OFFSET
1,18
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
EXAMPLE
For n = 4 = 2^2 there is no second smallest prime factor as 4 is a power of prime, therefore a(4) = 0.
For n = 18 = 2^1 * 3^2, the exponent of the second smallest prime factor (3) is 2, therefore a(18) = 2.
MATHEMATICA
Array[If[Length[#] < 2, 0, #[[2, -1]]] &@ FactorInteger[#] &, 108] (* Michael De Vlieger, Apr 01 2022 *)
PROG
(PARI) A351563(n) = if(1>=omega(n), 0, (factor(n))[2, 2]);
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 01 2022
STATUS
approved