OFFSET
1,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..352 (terms 1..322 from Ray Chandler)
C. Caldwell, Sigma function.
FORMULA
MATHEMATICA
DivisorSigma[1, 10^Range[20]-1] (* Harvey P. Dale, Jan 05 2012 *)
PROG
(PARI) a(n) = sigma(10^n-1); \\ Michel Marcus, Apr 22 2017
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.
KEYWORD
nonn
AUTHOR
Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Feb 14 2005
STATUS
approved