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A340369
a(n) = 1 if n has at most 3 prime factors when counted with multiplicity, 0 otherwise.
2
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1
OFFSET
1
FORMULA
a(n) = [A001222(n) <= 3], where [ ] is the Iverson bracket.
PROG
(PARI) A340369(n) = (bigomega(n)<=3);
CROSSREFS
Characteristic function of A037144.
Cf. A001222.
Cf. also A101040.
Sequence in context: A340372 A167850 A167851 * A307445 A363552 A307430
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 06 2021
STATUS
approved