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

Author

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

Keywords

• nonn

Links

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

Crossrefs

Cf. A000203, A002275, A070529.

Programs

Mathematica

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

PARI

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

Formula

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