OFFSET
1,2
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..352 (first 322 terms from Giovanni Resta)
EXAMPLE
n=60: concatenated distinct-prime factor-set for 60th-repunit is:
371113313741611012112412712161354190919901279612906161418890139526741,
its digit sum=a(60)=244.
MATHEMATICA
a[1]=0; a[n_] := Total[ Flatten[ IntegerDigits /@ First /@ FactorInteger[(10^n - 1)/9]]]; Array[a, 60] (* Giovanni Resta, Jul 19 2018 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Labos Elemer, Jun 22 2004
EXTENSIONS
Data corrected by Giovanni Resta, Jul 19 2018
STATUS
approved