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A309187 (1/8) times the number of n-member subsets of [8n] whose elements sum to a multiple of n. 2
1, 7, 85, 1127, 16451, 255619, 4141383, 69159399, 1182125128, 20581143157, 363704640476, 6506965279907, 117626432708864, 2145180354493281, 39421026305282660, 729242353169440743, 13568988503585900648, 253785064585174334488, 4768543107831461199897 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also (1/7) times the number of n-member subsets of [8n-1] whose elements sum to a multiple of n.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..768

FORMULA

a(n) = 1/(8n) * Sum_{d|n} binomial(8d,d)*(-1)^(n+d)*phi(n/d).

MAPLE

with(numtheory):

a:= n-> add(binomial(8*d, d)*(-1)^(n+d)*

        phi(n/d), d in divisors(n))/(8*n):

seq(a(n), n=1..25);

PROG

(PARI) a(n) = 1/(8*n) * sumdiv(n, d, binomial(8*d, d)*(-1)^(n+d)*eulerphi(n/d)); \\ Michel Marcus, Jul 18 2019

CROSSREFS

Column k=8 of A309148.

Sequence in context: A155631 A126344 A193578 * A026001 A064089 A216698

Adjacent sequences:  A309184 A309185 A309186 * A309188 A309189 A309190

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jul 15 2019

STATUS

approved

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Last modified November 13 17:34 EST 2019. Contains 329106 sequences. (Running on oeis4.)