A134211 -id:A134211 - cp's OEIS frontend

A133626 Numbers that are lunar products of exactly 2 lunar primes.

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, 397, 398, 399, 449, 459, 469

Offset: 1

N. J. A. Sloane, Aug 14 2010, Aug 16 2010

A subsequence of A087984.

David Applegate, Table of n, a(n) for n = 1..12319
David Applegate, Factorizations of all 9-ish numbers with <= 5 digits into products of lunar primes
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

Cf. A087097, A087984, A134211, A171004.

A087984 9-ish numbers (A011539) which are not lunar primes (A087097).

Original entry on oeis.org

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

Offset: 1

David Applegate and N. J. A. Sloane, Oct 30 2003

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).

M. F. Hasler, Table of n, a(n) for n = 1..10000
D. Applegate, C program for lunar arithmetic and number theory
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.
Index entries for sequences related to dismal (or lunar) arithmetic

Cf. A011539, A087097. A133626 and A134211 are subsequences.

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

is_A087984(n)=vecmax(digits(n))=9&&!is_A087097(n) \\ (End)

A011539 \ A087097. - M. F. Hasler, Nov 19 2018

cp's OEIS Frontend

A133626 Numbers that are lunar products of exactly 2 lunar primes.

Views

Author

Keywords

Comments

Links

Crossrefs