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A231821
a(n) = mu(n) + 3, where mu is the Mobius function (A008683).
2
4, 2, 2, 3, 2, 4, 2, 3, 3, 4, 2, 3, 2, 4, 4, 3, 2, 3, 2, 3, 4, 4, 2, 3, 3, 4, 3, 3, 2, 2, 2, 3, 4, 4, 4, 3, 2, 4, 4, 3, 2, 2, 2, 3, 3, 4, 2, 3, 3, 3, 4, 3, 2, 3, 4, 3, 4, 4, 2, 3, 2, 4, 3, 3, 4, 2, 2, 3, 4, 2, 2, 3, 2, 4, 3, 3, 4, 2, 2, 3, 3, 4, 2, 3, 4, 4
OFFSET
1,1
COMMENTS
If n is a prime or a semiprime, a(n) gives the number of divisors of n.
EXAMPLE
a(6) = 4; mu(6) + 3 = 1 + 3 = 4.
MAPLE
with(numtheory); a:=n->mobius(n)+3; seq(a(n), n=1..100);
MATHEMATICA
Table[MoebiusMu[n] + 3, {n, 100}]
PROG
(PARI) a(n) = moebius(n) + 3; \\ Michel Marcus, Nov 14 2013
(define (A231821 n) (+ 3 (A008683 n))) ;; Antti Karttunen, Jul 26 2017
CROSSREFS
Cf. A228409.
One more than A080847, two more than A007423.
Sequence in context: A049849 A376129 A112349 * A062072 A355849 A140395
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Nov 13 2013
STATUS
approved