%I #11 Jul 20 2019 08:10:35

%S 1,9,136,2289,42376,834336,17125354,362345361,7847250409,173103073384,

%T 3875837737520,87857163416064,2012268157890524,46497242493163450,

%U 1082614775186919136,25374686712458407441,598217593341171422090,14176230568946364963825

%N (1/10) times the number of n-member subsets of [10n] whose elements sum to a multiple of n.

%C Also (1/9) times the number of n-member subsets of [10n-1] whose elements sum to a multiple of n.

%H Alois P. Heinz, <a href="/A309189/b309189.txt">Table of n, a(n) for n = 1..712</a>

%F a(n) = 1/(10n) * Sum_{d|n} binomial(10d,d)*(-1)^(n+d)*phi(n/d).

%p with(numtheory):

%p a:= n-> add(binomial(10*d, d)*(-1)^(n+d)*

%p phi(n/d), d in divisors(n))/(10*n):

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

%o (PARI) a(n) = 1/(10*n) * sumdiv(n, d, binomial(10*d, d)*(-1)^(n+d)*eulerphi(n/d)); \\ _Michel Marcus_, Jul 20 2019

%Y Column k=10 of A309148.

%K nonn

%O 1,2

%A _Alois P. Heinz_, Jul 15 2019