OFFSET
1,6
COMMENTS
a(n) <= A095370(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
Max Alekseyev, Table of n, a(n) for n = 1..352 (first 322 terms from Giovanni Resta)
EXAMPLE
n=9: r9 = 111111111 = 3*3*37*333667, with a total of 9 digits among the distinct prime factors; the excess is a(9) = 9 - 9 = 0;
n=30: r30 = 111....1111 = 3*7*11*13*31*37*41*211*241*271*2161*9091*2906161, with a total of 36 digits among the distinct prime factors, so the excess a(30) = 36 - 30 = 6.
MATHEMATICA
a[1] = -1; a[n_] := Total[IntegerLength /@ First /@ FactorInteger[(10^n - 1)/9]] - n; Array[a, 60] (* Giovanni Resta, Jul 16 2018 *)
CROSSREFS
KEYWORD
sign,base
AUTHOR
Labos Elemer, Jun 22 2004
EXTENSIONS
Data corrected by Giovanni Resta, Jul 16 2018
STATUS
approved