A088574 Representative lunar primes.

19, 90, 99, 109, 901, 902, 909, 1009, 1019, 1029, 1091, 1092, 1099, 1109, 1209, 1901, 1902, 1909, 2019, 2091, 2109, 2901, 9001, 9009, 9011, 9012, 9019, 9021, 9091, 9099, 9101, 9102, 9109, 9201, 9901, 9909, 10009, 10019, 10029, 10091, 10092, 10099

Offset: 1

Author

N. J. A. Sloane and David Applegate, Nov 18 2003

Keywords

• nonn
• easy
• base

Comments

Let P = ...9..9ij...kl9...9... be a lunar prime (A087097), where the digits ij...kl are a typical string of consecutive digits that are not 9. Any number Q obtained from P by replacing ij...kl by other non-9-ish digits with the same order relationship as ij...kl is also prime. Sequence gives lexicographically earliest member of each such equivalence class.

It is necessary to consider order relations of all non-9 digits, not just consecutive ones. For example, 9091 is prime, but 9491 = 91*949. - David Wasserman, Aug 11 2005

Examples

			109, 209, 219, 309, 319, 329, 409, 419, ..., 879 are all lunar primes in the same class, ij9 with i>j, of which 109 is the earliest.
		

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

Crossrefs

Cf. A087097.

Extensions

More terms from David Wasserman, Aug 11 2005