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 A100448 Number of triples (i,j,k) with 1 <= i <= j < k <= n and GCD{i,j,k} = 1. 15
 0, 1, 4, 9, 19, 30, 51, 73, 106, 140, 195, 241, 319, 388, 480, 572, 708, 813, 984, 1124, 1310, 1485, 1738, 1926, 2216, 2462, 2777, 3059, 3465, 3749, 4214, 4590, 5060, 5484, 6048, 6474, 7140, 7671, 8331, 8899, 9719, 10289, 11192, 11902, 12754, 13535, 14616 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Probably the partial sums of A102309. - Ralf Stephan, Jan 03 2005 LINKS R. J. Mathar, Table of n, a(n) for n = 1..10000 FORMULA a(n) = (A071778(n)-1)/6. - Vladeta Jovovic, Nov 30 2004 (1/6) {-1 + sum[k=1..n, moebius(k)*floor(n/k)^3 ]. - Ralf Stephan, Jan 03 2005 MAPLE f:=proc(n) local i, j, k, t1, t2, t3; t1:=0; for i from 1 to n do for j from i to n do t2:=gcd(i, j); for k from j+1 to n do t3:=gcd(t2, k); if t3 = 1 then t1:=t1+1; fi; od: od: od: t1; end; MATHEMATICA f[n_] := Length[ Union[ Flatten[ Table[ If[ GCD[i, j, k] == 1, {i, j, k}], {i, n}, {j, i, n}, {k, j + 1, n}], 2]]]; Table[ If[n > 3, f[n] - 1, f[n]], {n, 47}] (* Robert G. Wilson v, Dec 14 2004 *) CROSSREFS Cf. A015616, A015631, A027430, A071778, A018805. Sequence in context: A184723 A075649 A199972 * A059820 A180784 A015618 Adjacent sequences:  A100445 A100446 A100447 * A100449 A100450 A100451 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Nov 21 2004 EXTENSIONS More terms from Robert G. Wilson v, Dec 14 2004 Edited by N. J. A. Sloane, Sep 06 2008 at the suggestion of R. J. Mathar STATUS approved

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