A169982 Maximal number of lunar divisors of any 9-ish number with n digits.

1, 2, 4, 14, 41, 222

Offset

1,2

Links

Table of n, a(n) for n=1..6.

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]

Index entries for sequences related to dismal (or lunar) arithmetic

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

Cf. A169983 (which is a lower bound).

Sequence in context: A000912 A228477 A360182 * A367101 A243323 A128750

Adjacent sequences: A169979 A169980 A169981 * A169983 A169984 A169985

Keyword

nonn,base,more

Author

David Applegate, Marc LeBrun and N. J. A. Sloane, Aug 21 2010

Status

approved