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A087097 Lunar primes (formerly called dismal primes) (cf. A087062). 26
19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 109, 209, 219, 309, 319, 329, 409, 419, 429, 439, 509, 519, 529, 539, 549, 609, 619, 629, 639, 649, 659, 709, 719, 729, 739, 749, 759, 769, 809, 819, 829, 839, 849, 859, 869, 879, 901, 902, 903, 904, 905, 906, 907, 908, 909, 912, 913, 914, 915, 916, 917, 918, 919, 923, 924, 925, 926, 927, 928, 929, 934, 935, 936, 937, 938, 939, 945, 946, 947, 948, 949, 956, 957, 958, 959, 967, 968, 969, 978, 979, 989 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

9 is the multiplicative unit. A number n is a lunar prime if it is not a lunar product (see A087062 for definition) r*s where neither r nor s is 9.

All lunar primes must contain a 9, so this is a subset of A011539.

Also, numbers n such that the lunar sum of the lunar prime divisors of n is n. - N. J. A. Sloane, Aug 23 2010

We have changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing. - N. J. A. Sloane, Aug 06 2014

LINKS

David Applegate and N. J. A. Sloane, Table of n, a(n) for n = 1..22095 [all primes with at most 5 digits]

D. Applegate, C program for lunar arithmetic and number theory

D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic

Brady Haran and N. J. A. Sloane, Primes on the Moon (Lunar Arithmetic), Numberphile video, Nov 2018.

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

EXAMPLE

8 is not prime since 8 = 8*8. 9 is not prime since it is the multiplicative unit. 10 is not prime since 10 = 10*8. Thus 19 is the smallest prime.

CROSSREFS

Cf. A087019, A087061, A087062, A087636, A087638, A087984.

Sequence in context: A047985 A061763 A088474 * A038364 A151360 A109276

Adjacent sequences:  A087094 A087095 A087096 * A087098 A087099 A087100

KEYWORD

nonn,easy,base,changed

AUTHOR

Marc LeBrun, Oct 20 2003

STATUS

approved

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Last modified November 16 12:40 EST 2018. Contains 317272 sequences. (Running on oeis4.)