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A309185 (1/6) times the number of n-member subsets of [6n] whose elements sum to a multiple of n. 2

%I #10 Jul 18 2019 10:15:43

%S 1,5,46,445,4751,54086,642342,7861661,98480332,1256564755,16273981758,

%T 213378975958,2826867619109,37782552518478,508840821830546,

%U 6898459216311581,94070535317459018,1289430373107971804,17755914760643605782,245518560760433579195

%N (1/6) times the number of n-member subsets of [6n] whose elements sum to a multiple of n.

%C Also (1/5) times the number of n-member subsets of [6n-1] whose elements sum to a multiple of n.

%H Alois P. Heinz, <a href="/A309185/b309185.txt">Table of n, a(n) for n = 1..856</a>

%F a(n) = 1/(6n) * Sum_{d|n} binomial(6d,d)*(-1)^(n+d)*phi(n/d).

%p with(numtheory):

%p a:= n-> add(binomial(6*d, d)*(-1)^(n+d)*

%p phi(n/d), d in divisors(n))/(6*n):

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

%Y Column k=6 of A309148.

%K nonn

%O 1,2

%A _Alois P. Heinz_, Jul 15 2019

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Last modified March 28 08:02 EDT 2024. Contains 371236 sequences. (Running on oeis4.)