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A084846
mu(n!+1), where mu is the Moebius function (A008683).
4
-1, -1, -1, -1, 0, 0, 1, 0, 1, -1, 1, -1, 0, 1, 1, -1, -1, -1, 1, 1, 1, -1, -1, 0, 1, 1, 1, -1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1, 1, -1, -1, -1, 1, -1, -1, -1, 1, 1, -1, -1, 1, 1, 1, 1, 1, 1, -1, 1, 1, 1, 1, -1, -1, -1, 1, -1, 1, -1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, -1, -1, -1, -1, -1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, -1, 1, 1, -1, -1, 1, -1, 1, 1, 1, 1, -1, 1, 1, 1, 1, 1, -1, 1
OFFSET
0,1
LINKS
Paul Leyland, Factors of n!+1.
Markus Tervooren et al., Factorization of n!+1, FactorDB.
FORMULA
If n is in A064237, then a(n) = 0. Otherwise a(n) = (-1)^A054990(n) = (-1)^A066856(n). - Max Alekseyev, Oct 08 2019
EXAMPLE
a(6)=1 because 6!+1 = 721 = 7 * 103, the product of two different primes and thus mu(6!+1) = (-1)^2 = 1.
PROG
(Magma) [MoebiusMu(Factorial(n)+1) : n in [1..45]];
(PARI) for(n=0, 45, print1(moebius(n!+1), ", "))
CROSSREFS
Cf. A008683 (mu(n)), A054990 (bigomega(n!+1)), A066856 (omega(n!+1)), A064237 (n!+1 divisible by a square), A002981 (n!+1 is prime).
Sequence in context: A130657 A347871 A185916 * A285498 A285504 A130093
KEYWORD
hard,sign
AUTHOR
Rick L. Shepherd, Jun 10 2003
EXTENSIONS
a(112) corrected, a(113)-a(114) added by Max Alekseyev, May 28 2015
a(106)-a(107) corrected by Amiram Eldar, Oct 03 2019
STATUS
approved