OFFSET
1,2
EXAMPLE
For n = 10 we have a(n-1) = a(9) = 9; removing 9 from 9*n = 9*10 = 90 results in one remaining digit (i.e. 0) and for every smaller multiple of 10 (i.e. 10, 20, ..., 80) there are two remaining digits, so a(10) = 90. For n = 20 we have a(n-1) = a(19) = 19; for 1*n = 1*20 = 20 no digit is removed and two digits remain and there is no multiple of 20 which has less than two remaining digits (for 100 twice the digit 0), so a(20) = 20.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 21 2002
EXTENSIONS
Edited, corrected and extended by Klaus Brockhaus, Dec 03 2002
STATUS
approved