A179307 a(n) = Sum_{d|n} C(n,d)*sigma(d)*sigma(n/d).

1, 9, 16, 89, 36, 504, 64, 2193, 1474, 5544, 144, 56024, 196, 84912, 83376, 674257, 324, 2833128, 400, 10842624, 3764224, 25404696, 576, 283622136, 1913486, 436839984, 243868120, 2955876880, 900, 13385040624, 1024, 57008721777, 9290026080, 126014768064, 338361024

Offset

1,2

Comments

Logarithmic derivative of A179306.

Links

Table of n, a(n) for n=1..35.

Mathematica

a[n_] := DivisorSum[n, Binomial[n, #] * DivisorSigma[1, #] * DivisorSigma[1, n/#] &]; Array[a, 35] (* Amiram Eldar, Aug 18 2023 *)

Prog

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

Crossrefs

Cf. A000203, A179306.

Sequence in context: A267763 A340164 A308248 * A014720 A378060 A138238

Adjacent sequences: A179304 A179305 A179306 * A179308 A179309 A179310

Keyword

nonn

Author

Paul D. Hanna, Jul 10 2010

Extensions

a(33)-a(35) from Amiram Eldar, Aug 18 2023

Status

approved