

A087984


9ish numbers (A011539) which are not lunar primes (A087097).


4



9, 119, 129, 139, 149, 159, 169, 179, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 229, 239, 249, 259, 269, 279, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 339, 349, 359, 369, 379, 389, 390, 391, 392, 393, 394, 395, 396
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OFFSET

1,1


COMMENTS

Three and four digit 9ish numbers are lunar primes iff the smallest digit is strictly smaller than the first and the last digit. This is no longer true from 10109 = 109 x 109 on (where x = lunar product).


LINKS

D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic, preprint, arxiv:1107.1130, July 2011. [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic"  the old name was too depressing.]
D. Applegate, M. LeBrun, N. J. A. Sloane, Dismal Arithmetic, J. Int. Seq. 14 (2011) # 11.9.8.


FORMULA



PROG

A087984=[9]; for(L=3, 4, forvec(d=vector(L, i, [i==1, 9]), vecmax(d)==9&&vecmin(d)>=min(d[1], d[L])&&A087984=concat(A087984, fromdigits(d)))) \\ terms with < 5 digits


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



