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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If n is a prime or a semiprime, a(n) gives the number of divisors of n. LINKS Antti Karttunen, Table of n, a(n) for n = 1..5000 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: A037919 A049849 A112349 * A062072 A140395 A061505 Adjacent sequences:  A231818 A231819 A231820 * A231822 A231823 A231824 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, Nov 13 2013 STATUS approved

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Last modified October 21 06:39 EDT 2019. Contains 328292 sequences. (Running on oeis4.)