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A087984 9-ish 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 (list; graph; refs; listen; history; text; internal format)
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
A011539 \ A087097. - M. F. Hasler, Nov 19 2018
PROG
From M. F. Hasler, Nov 19 2018: (Start)
(PARI) A087984=setminus(A011539, A087097)
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
(PARI) is_A087984(n)=vecmax(digits(n))=9&&!is_A087097(n) \\ (End)
CROSSREFS
Cf. A011539, A087097. A133626 and A134211 are subsequences.
Sequence in context: A166823 A322928 A340236 * A197544 A234964 A210046
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified June 15 11:14 EDT 2024. Contains 373407 sequences. (Running on oeis4.)