OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..402
FORMULA
MATHEMATICA
DivisorSigma[1, (8^Range[20]-1)/7] (* Harvey P. Dale, Aug 21 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Mar 31 2005
STATUS
approved