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A259446
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Number of triangles with sides pairwise relatively prime and no greater than n; permutations of sides are not considered distinct.
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2
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1, 1, 1, 1, 2, 2, 5, 7, 11, 12, 23, 25, 42, 48, 56, 65, 97, 103, 145, 157, 179, 194, 258, 270, 326, 351, 400, 425, 532, 544, 668, 719, 783, 828, 914, 941, 1121, 1180, 1271, 1316, 1541, 1571, 1821, 1902, 1998, 2085, 2387, 2442, 2705, 2787
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OFFSET
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1,5
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LINKS
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EXAMPLE
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(1,1,1) is the only triangle up to n=4; (3,4,5) is added for n=5 and n=6.
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MATHEMATICA
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triangles[n_] := Module[{count = 0},
For[a = 1, a <= n, a++,
For[b = a, b <= n, b++,
For[c = b, c <= n, c++,
If[(a + b > c) && (b + c > a) && (c + a > b) && CoprimeQ[a, b, c],
count++]]]];
count];
triangles[#] & /@ Range[50]
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PROG
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(PARI) a(n)=sum(a=3, n-2, sum(b=a+1, n-1, if(gcd(a, b)==1, sum(c=b+1, min(a+b-1, n), gcd(a*b, c)==1))))+1 \\ Charles R Greathouse IV, Jun 29 2015
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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