OFFSET
1,2
LINKS
D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing]
EXAMPLE
At length 1, 9 has one divisor, 9 itself.
At length 2, all 18 9-ish numbers N are lunar primes and therefore have two divisors, 9 and N.
At length 3, 998 and many others have 4 divisors.
At length 4, just 4 numbers have 14 divisors, namely 9988, 8988, 8899, 8898.
At length 5, there is a unique number with 41 divisors, 88988.
At length 9, there is a unique number with 222 divisors, 99999.
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
STATUS
approved