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 A087028 Number of bounded (<=n) lunar divisors of n. 4
 1, 1, 1, 1, 1, 1, 1, 1, 1, 10, 10, 9, 8, 7, 6, 5, 4, 3, 2, 9, 9, 9, 8, 7, 6, 5, 4, 3, 2, 8, 8, 8, 8, 7, 6, 5, 4, 3, 2, 7, 7, 7, 7, 7, 6, 5, 4, 3, 2, 6, 6, 6, 6, 6, 6, 5, 4, 3, 2, 5, 5, 5, 5, 5, 5, 5, 4, 3, 2, 4, 4, 4, 4, 4, 4, 4, 4, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 19, 10, 9, 8, 7, 6, 5, 4, 3, 2, 100, 91, 17, 15, 13, 11, 9, 7, 5, 3, 25, 25, 81, 22, 19, 16, 13, 10, 7, 4, 22, 22, 22, 64, 19, 16, 13, 10, 7, 4, 19, 19, 19, 19, 49, 16, 13, 10, 7, 4, 16, 16, 16, 16, 16, 36, 13, 10, 7, 4, 13, 13, 13, 13, 13, 13, 25, 10, 7, 4, 10, 10, 10, 10, 10, 10, 10, 16, 7, 4, 7, 7, 7, 7, 7, 7, 7, 7, 9, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 17 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,10 COMMENTS Number of d, 1 <= d <= n, such that there exists an e, 1 <= e <= n, with d*e = n, where * is lunar multiplication. LINKS D. Applegate, Table of n, a(n) for n = 1..100000 D. Applegate, C program for lunar arithmetic and number theory [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 [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing] EXAMPLE The 10 divisors of 10 <= 10 are 1, 2, ..., 9, 10. a(100) = 19, since the lunar divisors of 100 <= 100 are 1, 2, ..., 9, 10, 20, ..., 90, 100. MAPLE (Uses programs from A087062) dd1 := proc(n) local t1, t2, i, j; t1 := []; for i from 1 to n do for j from i to n do if dmul(i, j) = n then t1 := [op(t1), i, j]; fi; od; od; t1 := convert(t1, set); t2 := sort(convert(t1, list)); nops(t2); end; CROSSREFS Cf. A087029, A087082. Sequence in context: A112120 A099401 A263450 * A145279 A103708 A239051 Adjacent sequences:  A087025 A087026 A087027 * A087029 A087030 A087031 KEYWORD nonn,easy,base AUTHOR Marc LeBrun and N. J. A. Sloane, Oct 19 2003 STATUS approved

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Last modified May 23 07:54 EDT 2022. Contains 353961 sequences. (Running on oeis4.)