OFFSET
1,4
COMMENTS
Also products of terms in rows of A047996.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..50
R. Bekes, J. Pedersen and B. Shao, Mad tea party cyclic partitions, College Math. J., 43 (2012), 24-36.
MAPLE
with (numtheory):
a:= n-> mul (add(phi(d)*binomial(n/d, k/d),
d=divisors(igcd(n, k))), k=0..n)/n^(n+1):
seq (a(n), n=1..20); # Alois P. Heinz, Sep 06 2012
MATHEMATICA
t[n_, k_] := Total[EulerPhi[#] * Binomial[n/#, k/#]& /@ Divisors[GCD[n, k]]]/n; Table[Times @@ Table[t[n, k], {k, 1, n}], {n, 1, 18}] (* Jean-François Alcover, Mar 07 2014 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Sep 05 2012
STATUS
approved