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A353676
a(n) = 1 if n is an odd number with exactly 2 distinct prime factors, otherwise 0.
3
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0
OFFSET
1
FORMULA
a(n) = A000035(n) * A215480(n).
A353675(n) >= a(n) >= A353677(n).
EXAMPLE
n = 45 = 3^2 * 5 is an odd number with two distinct prime factors, therefore a(45) = 1.
PROG
(PARI) A353676(n) = ((n%2) && (2==omega(n)));
CROSSREFS
Characteristic function of A225375.
After n=1 differs from A353675 for the next time at n=1155, where a(1155)=0, while A353675(1155)=1.
Sequence in context: A277161 A353481 A353677 * A340370 A216038 A011728
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 03 2022
STATUS
approved