OFFSET
0,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..10000
FORMULA
Equals Sum_{k>=1} d(k)/5^k, where d(k) is the number of divisors of k (A000005). - Amiram Eldar, Jun 22 2020
EXAMPLE
0.301733853597972457948162159393991192623009431517157720395791923318379825892...
MAPLE
evalf( add( (1/5)^(n^2)*(1 + 2/(5^n - 1)), n = 1..12), 105); # Peter Bala, Jan 30 2022
MATHEMATICA
x = 1/5; RealDigits[ Sum[ DivisorSigma[0, k] x^k, {k, 1000}], 10, 105][[1]] (* after an observation and the formula of Amarnath Murthy, see A073668 *)
PROG
(PARI) sumpos(k=1, 1/(5^k-1)) \\ M. F. Hasler, Oct 15 2014
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Robert G. Wilson v, Oct 12 2014
STATUS
approved