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%I #12 Dec 13 2017 00:17:08
%S 1,2,4,11,28,152,726,5268,40438,365944,3628810,39974466,479001612,
%T 6228256404,87178339984,1307706805928,20922789888016,355688409760972,
%U 6402373705728018,121645133931170028,2432902008232456692
%N Variant of A061417.
%C Does this count some variety of necklaces?
%H G. C. Greubel, <a href="/A061860/b061860.txt">Table of n, a(n) for n = 0..445</a>
%F a(n) = (1/n)*Sum_{d|n} phi(n/d)*C(n, d)*(d!).
%p [seq(A061860(j),j=1..40)]; with(numtheory); A061860 := proc(n) local d,s; s := 0; for d in divisors(n) do s := s + phi(n/d)*(binomial(n,d))*(d!); od; RETURN(s/n); end;
%t a[n_] := DivisorSum[n, EulerPhi[n/#] Binomial[n, #] (#!)&]/n; Array[a, 25] (* _Jean-François Alcover_, Mar 06 2016 *)
%Y A061860[p] = A061417[p] = (p-1)!+(p-1) for all prime p's.
%K nonn
%O 0,2
%A _Antti Karttunen_, May 11 2001
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