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URL: https://oeis.org/A087636

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A087636
Number of n-digit lunar primes.
7
0, 18, 81, 1539, 20457, 242217, 2894799, 33535839, 381591711
OFFSET
1,2
COMMENTS
Although a(1) through a(6) are divisible by 9, a(7) is not.
LINKS
D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic, arxiv:1107.1130 [math.NT], 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, and N. J. A. Sloane, Dismal Arithmetic, J. Int. Seq. 14 (2011) # 11.9.8.
Benjamin Baily, Justine Dell, Henry L. Fleischmann, Faye Jackson, Steven J. Miller, Ethan Pesikoff, and Luke Reifenberg, Irreducibility over the max-min semiring, arXiv:2111.09786 [math.CO], 2021.
PROG
(PARI) A87636=[]; A087636(n)={while(#A87636<n, A87636=concat(A87636, 0)); !A87636[n] && A87636[n]=sum(k=10^(n-1), 10^n-1, is_A087097(k)); A87636[n]} \\ Store results in array A87636 to avoid re-calculation. - M. F. Hasler, Nov 15 2018
CROSSREFS
Cf. A087062 (lunar product), A087097 (lunar primes), A087638 (partial sums).
Sequence in context: A214531 A271502 A235641 * A156218 A118293 A043430
KEYWORD
nonn,base,more
AUTHOR
Marc LeBrun and N. J. A. Sloane, Oct 26 2003
EXTENSIONS
a(6)-a(9) from David Applegate, Nov 07 2003
STATUS
approved