OFFSET
1,6
COMMENTS
a(n) <= A055642(n) + A001221(n) - 1 since the product of a k digit number and an m digit number has at least k+m-1 digits. - Chai Wah Wu, Nov 03 2019
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
n=22: prime set={2,11}, a[22]=1+2=3.
MATHEMATICA
Prepend[(Total [ Length[IntegerDigits[#]] & /@ ( #[[1]] & /@ FactorInteger[#])] & /@ Range[2, 105]), 0] (* Zak Seidov, Aug 26 2016 *)
PROG
(PARI) a(n)=vecsum(apply(p->#Str(p), factor(n)[, 1])) \\ Charles R Greathouse IV, Aug 26 2016
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Labos Elemer, Jun 21 2004
STATUS
approved