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A218256 a(n) = |{m : multiplicative order of n mod m = 7}|. 3
0, 1, 2, 6, 3, 2, 12, 10, 12, 9, 12, 6, 6, 2, 8, 60, 5, 6, 18, 14, 42, 8, 12, 14, 56, 3, 12, 12, 12, 14, 8, 14, 18, 12, 12, 44, 27, 2, 12, 4, 24, 6, 40, 14, 42, 6, 12, 6, 150, 5, 18, 60, 18, 14, 24, 4, 40, 12, 60, 2, 12, 6, 12, 138, 49, 4, 24, 2, 18, 12, 40, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = tau(n^7-1)-tau(n-1), with tau = A000005.

MAPLE

with(numtheory):

a:= n-> add(mobius(7/d) *tau(n^d-1), d={1, 7}):

seq(a(n), n=1..80);

CROSSREFS

Row n=7 of A212957.

Cf. A000005, A008683.

Sequence in context: A138054 A297927 A321873 * A198418 A086360 A066098

Adjacent sequences:  A218253 A218254 A218255 * A218257 A218258 A218259

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Oct 24 2012

STATUS

approved

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Last modified July 7 16:01 EDT 2020. Contains 335496 sequences. (Running on oeis4.)