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Search: id:A100448
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| A100448 |
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Number of triples (i,j,k) with 1 <= i <= j < k <= n and GCD{i,j,k} = 1. |
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+0
4
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| 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; listen)
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OFFSET
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1,3
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FORMULA
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a(n) = (A071778(n)-1)/6. - Vladeta Jovovic (vladeta(AT)Eunet.yu), Nov 30 2004
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MAPLE
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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;
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MATHEMATICA
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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}] (from Robert G. Wilson v Dec 14 2004)
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CROSSREFS
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Cf. A015616, A015631, A027430, A071778, A018805.
Sequence in context: A045278 A075649 A102308 this_sequence A059820 A015618 A086733
Adjacent sequences: A100445 A100446 A100447 this_sequence A100449 A100450 A100451
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KEYWORD
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nonn,easy
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AUTHOR
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njas, Nov 21 2004
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 14 2004
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