A231821 a(n) = mu(n) + 3, where mu is the Mobius function (A008683).

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.

Links

Antti Karttunen, Table of n, a(n) for n = 1..5000

Index entries for sequences computed from exponents in factorization 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: A037919 A049849 A112349 * A062072 A355849 A140395

Adjacent sequences: A231818 A231819 A231820 * A231822 A231823 A231824

Keyword

nonn,easy

Author

Wesley Ivan Hurt, Nov 13 2013

Status

approved