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A088574
Representative lunar primes.
1
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
1,1
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
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
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.
CROSSREFS
Cf. A087097.
Sequence in context: A160296 A347364 A224097 * A096031 A302710 A157875
KEYWORD
nonn,easy,base
AUTHOR
EXTENSIONS
More terms from David Wasserman, Aug 11 2005
STATUS
approved