A215251 Product of terms in n-th row of A037306.

1, 1, 1, 2, 4, 36, 225, 7840, 313600, 45302400, 8930250000, 8373836401920, 9001015156742400, 41813367543204433176, 325385777102562972821025, 8270190445766978650521600000, 377177413291384771899817984000000, 62187743659065606074696974956949929984

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

Cf. A037306, A008965, A047996.

Sequence in context: A182965 A189002 A304558 * A052716 A081976 A326932

Adjacent sequences: A215248 A215249 A215250 * A215252 A215253 A215254

Keyword

nonn,easy

Author

N. J. A. Sloane, Sep 05 2012

Status

approved