A103968 Sigma((8^n - 1)/7), where sigma(n) is the sum of positive divisors of n.

1, 13, 74, 1092, 4864, 59200, 346112, 4756752, 19436692, 251916288, 1294876800, 20786304000, 79541043200, 1073030266880, 5303003316224, 81061789640832, 324992122224640, 4102172934143680, 20588576135708672, 376372958524932096

Offset: 1

Author

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Mar 31 2005

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..402

Crossrefs

Cf. A000203, A023001.

Programs

Mathematica

DivisorSigma[1,(8^Range[20]-1)/7] (* Harvey P. Dale, Aug 21 2011 *)

Formula

a(n) = A000203(A023001(n)). - Amiram Eldar, Feb 24 2020