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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
OFFSET
1,3
LINKS
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.
Sequence in context: A138054 A297927 A321873 * A198418 A086360 A066098
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 24 2012
STATUS
approved