A359796 a(n) = Sum_{d|n} (2*d)^(d-1).

1, 5, 37, 517, 10001, 248873, 7529537, 268435973, 11019960613, 512000010005, 26559922791425, 1521681143418409, 95428956661682177, 6502111422505477189, 478296900000000010037, 37778931862957430145541, 3189059870763703892770817

Offset

1,2

Links

Table of n, a(n) for n=1..17.

Formula

G.f.: Sum_{k>0} (2 * k)^(k-1) * x^k / (1 - x^k).

Mathematica

a[n_] := DivisorSum[n, (2*#)^(# - 1) &]; Array[a, 20] (* Amiram Eldar, Aug 14 2023 *)

Prog

(PARI) a(n) = sumdiv(n, d, (2*d)^(d-1));
(PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, (2*k)^(k-1)*x^k/(1-x^k)))

Crossrefs

Cf. A262843, A359731.

Sequence in context: A286928 A321042 A244820 * A360933 A246534 A095957

Adjacent sequences: A359793 A359794 A359795 * A359797 A359798 A359799

Keyword

nonn,easy

Author

Seiichi Manyama, Jan 13 2023

Status

approved