A102146 a(n) = sigma(10^n - 1), where sigma(n) is the sum of positive divisors of n.

13, 156, 1520, 15912, 148512, 2042880, 14508000, 162493344, 1534205464, 16203253248, 144451398000, 2063316971520, 14903272088640, 158269280832000, 1614847741624320, 17205180696931968, 144444514193267496

Offset: 1

Author

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Feb 14 2005

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..352 (terms 1..322 from Ray Chandler)
• C. Caldwell, Sigma function.

Crossrefs

Cf. A000203, A001270, A002283, A003020, A005422, A046053, A046107, A046412, A046415, A046416, A046417, A046418, A046419, A046420, A057951, A059892, A061075, A070528, A070529, A081317, A081318, A085035, A095370, A095413, A095414, A095417, A095418, A102347, A102380, A112505, A147556, A295503, A366669.

Programs

Mathematica

DivisorSigma[1,10^Range[20]-1] (* Harvey P. Dale, Jan 05 2012 *)

PARI

a(n) = sigma(10^n-1); \\ Michel Marcus, Apr 22 2017

Formula

a(n) = A000203(A002283(n)). - Ray Chandler, Apr 22 2017