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A249904
a(n) = mu(n) + sigma(n) - n.
1
1, 0, 0, 3, 0, 7, 0, 7, 4, 9, 0, 16, 0, 11, 10, 15, 0, 21, 0, 22, 12, 15, 0, 36, 6, 17, 13, 28, 0, 41, 0, 31, 16, 21, 14, 55, 0, 23, 18, 50, 0, 53, 0, 40, 33, 27, 0, 76, 8, 43, 22, 46, 0, 66, 18, 64, 24, 33, 0, 108, 0, 35, 41, 63, 20, 77
OFFSET
1,4
COMMENTS
The 0 terms identify the prime numbers.
LINKS
FORMULA
a(n) = A001065(n) + A008683(n). - Antti Karttunen, Feb 25 2018
MATHEMATICA
Table[(MoebiusMu[k] + (DivisorSigma[1, k] - k)), {k, 200} ]
PROG
(PARI) vector(100, n, moebius(n) + sigma(n) - n) \\ Michel Marcus, Jan 31 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Ke Xiao, Jan 13 2015
STATUS
approved