OFFSET
1,2
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..352 (first 322 terms from Giovanni Resta)
FORMULA
a(n) < A095370(n) + n. - Chai Wah Wu, Nov 04 2019
EXAMPLE
n=10: 10th repunit = 1111111111 = 11*41*271*9091; distinct prime factors have a total of 11 decimal digits, so a(10)=11.
n=27: 27th repunit = 111111111111111111111111111 = 3^3*37*757*333667*440334654777631, with 28 prime factor digits, a(27)=28.
MATHEMATICA
a[1] = 0; a[n_] := Total[IntegerLength /@ First /@ FactorInteger[(10^n - 1) /9]]; Array[a, 70] (* Giovanni Resta, Jul 09 2018 *)
PROG
(PARI) a(n) = vecsum(apply(x->#Str(x), factor((10^n-1)/9)[, 1])); \\ Michel Marcus, Jul 09 2018
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Labos Elemer, Jun 22 2004
STATUS
approved