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A054614
a(n) = Sum_{d|n} phi(d)*7^(n/d).
3
0, 7, 56, 357, 2464, 16835, 118104, 823585, 5767328, 40354335, 282492280, 1977326813, 13841410464, 96889010491, 678223896728, 4747561544985, 33232936339456, 232630513987319, 1628413638500376, 11398895185373269
OFFSET
0,2
LINKS
FORMULA
a(n) = Sum_{k=1..n} 7^gcd(n,k). - Ilya Gutkovskiy, Apr 16 2021
PROG
(PARI) a(n) = sumdiv(n, d, eulerphi(d)*7^(n/d)); \\ Michel Marcus, Jul 11 2021
CROSSREFS
Column k=7 of A185651.
Cf. A054626.
Sequence in context: A180287 A082140 A264693 * A270240 A344066 A104896
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 16 2000
STATUS
approved