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A185953
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Number of pairwise coprime triples of positive integers with largest element n (i.e., A015617(n) - A015617(n-1)).
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6
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0, 0, 1, 1, 5, 1, 11, 6, 12, 5, 31, 6, 45, 14, 21, 24, 79, 15, 101, 27, 49, 37, 149, 28, 126, 56, 109, 57, 241, 28, 277, 106, 137, 100, 183, 62, 395, 128, 193, 102, 489, 65, 541, 165, 203, 189, 649, 116, 551, 170, 347, 231, 829, 147, 506, 234, 434, 307, 1027, 119, 1101, 364, 450, 412, 727
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OFFSET
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1,5
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REFERENCES
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Robert Israel, Posting to Sequence Fans Mailing List, Feb 06, 2011
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LINKS
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MATHEMATICA
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a[n_] := Sum[Boole[GCD[a, n] == 1 && GCD[b, n] == 1 && GCD[a, b] == 1], {a, 1, n-2}, {b, a+1, n-1}]; Array[a, 100] (* Jean-François Alcover, Mar 05 2019, from PARI *)
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PROG
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(PARI) a(n)=sum(a=1, n-2, sum(b=a+1, n-1, gcd(a, n)==1&&gcd(b, n)==1&&gcd(a, b)==1)) \\ Charles R Greathouse IV, Apr 28 2015
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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