A306842 a(n) = Sum_{d|n} binomial(n,d)*binomial(n,n/d).

1, 4, 6, 44, 10, 612, 14, 3936, 7074, 22700, 22, 339792, 26, 624652, 2732760, 6401232, 34, 45174204, 38, 220441080, 309304842, 325909628, 46, 7330314960, 2822796950, 6760390052, 27417926304, 78814587656, 58, 548150764560, 62, 1352747882944, 2111872688706

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..3000

Formula

If p is prime, a(p) = 2*p.

Mathematica

a[n_] := DivisorSum[n, Binomial[n, #] * Binomial[n, n/#] &]; Array[a, 30] (* Amiram Eldar, Jun 13 2021 *)

Prog

(PARI) {a(n) = sumdiv(n, d, binomial(n, d)*binomial(n, n/d))}

Crossrefs

Cf. A100484, A174462.

Sequence in context: A034923 A013022 A012908 * A284634 A077100 A012935

Adjacent sequences: A306839 A306840 A306841 * A306843 A306844 A306845

Keyword

nonn

Author

Seiichi Manyama, Mar 12 2019

Status

approved