A218124 Number of 7-ary sequences with primitive period n.

1, 7, 42, 336, 2352, 16800, 117264, 823536, 5762400, 40353264, 282458400, 1977326736, 13841167200, 96889010400, 678222249264, 4747561492800, 33232924804800, 232630513987200, 1628413557439536, 11398895185373136, 79792266015134400, 558545864082460128

Offset

0,2

Links

Alois P. Heinz, Table of n, a(n) for n = 0..400

Formula

a(n) = Sum_{d|n} 7^d * mu(n/d) for n>0, a(0) = 1.

G.f.: 1 + 7 * Sum_{k>=1} mu(k) * x^k / (1 - 7*x^k). - Ilya Gutkovskiy, Apr 14 2021

Maple

with(numtheory):
a:= n-> `if`(n=0, 1, add(7^d *mobius(n/d), d=divisors(n))):
seq(a(n), n=0..30);

Crossrefs

Column k=7 of A143324.

Sequence in context: A271427 A073506 A025593 * A048862 A208943 A209071

Adjacent sequences: A218121 A218122 A218123 * A218125 A218126 A218127

Keyword

nonn

Author

Alois P. Heinz, Oct 21 2012

Status

approved