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 A117108 Moebius transform of tetrahedral numbers. 0
 1, 3, 9, 16, 34, 43, 83, 100, 155, 182, 285, 292, 454, 473, 636, 696, 968, 929, 1329, 1304, 1678, 1735, 2299, 2136, 2890, 2818, 3489, 3484, 4494, 4052, 5455, 5168, 6250, 6168, 7652, 6988, 9138, 8547, 10196, 9840, 12340, 10954, 14189, 13140, 15380 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Partial sums of a(n) give A015634(n). See also A116963, inverse Moebius transform of tetrahedral numbers. - Jonathan Vos Post, Apr 20 2006 LINKS FORMULA a(n) = |{(x,y,z) : 1 <= x <= y <= z <= n, gcd(x,y,z,n) = 1}|. EXAMPLE a(2)=3 because of the triples (1,1,1), (1,1,2), (1,2,2). PROG (PARI) a(n) = sumdiv(n, d, binomial(d+2, 3)*moebius(n/d)); \\ Michel Marcus, Nov 04 2018 CROSSREFS Cf. A000292 (tetrahedral numbers), A015634 (partial sums), A116963. Sequence in context: A232167 A058538 A197531 * A223188 A145796 A056403 Adjacent sequences:  A117105 A117106 A117107 * A117109 A117110 A117111 KEYWORD nonn AUTHOR Steve Butler, Apr 18 2006 STATUS approved

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Last modified May 22 21:03 EDT 2019. Contains 323500 sequences. (Running on oeis4.)