A103759 a(n) = sigma((10^n - 1)/9), where sigma(n) is the sum of positive divisors of n.

1, 12, 152, 1224, 11424, 204288, 1116000, 12499488, 164831992, 1246404096, 11111646000, 206331697152, 1146405545280, 12174560064000, 161484774162432, 1323475438225536, 11111116476405192, 232965361825996800

Offset

1,2

Links

Ray Chandler, Table of n, a(n) for n = 1..322

Formula

a(n) = A000203(A002275(n)). - Michel Marcus, Sep 08 2015

Mathematica

Table[DivisorSigma[1, FromDigits[PadRight[{}, n, 1]]], {n, 20}] (* Harvey P. Dale, Jul 13 2022 *)

Prog

(PARI) a(n) = sigma((10^n - 1)/9); \\ Michel Marcus, Sep 08 2015

Crossrefs

Cf. A000203, A002275, A070529.

Sequence in context: A127650 A286432 A189548 * A351526 A121195 A189490

Adjacent sequences: A103756 A103757 A103758 * A103760 A103761 A103762

Keyword

nonn

Author

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Mar 28 2005

Status

approved