OFFSET
1,2
FORMULA
a(1) = 1. For n > 1, let k = floor(1+log_10(n)); then a(n) = n*(10^(k*a(n-1))-1)/(10^k-1).
EXAMPLE
a(1) says: there will be one 2 in a(2).
a(2)=2 because a(1) said so; and a(2)=2 says: there will be two 3's in a(3).
a(3)=33 because a(2) said so; and also a(3) says: there will be thirty three 4's in a(4).
Therefore a(4)= 444444444444444444444444444444444 (33 times the digit 4).
And a(5)= 555555555555555...555 (with 444444444444444444444444444444444 5's).
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Alexandre Wajnberg, Aug 23 2005
EXTENSIONS
Formula corrected to handle n>9 also by Rick L. Shepherd, Mar 22 2009
STATUS
approved