A103759 - OEIS

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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

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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