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A308224
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Sum of the largest sides of all integer-sided triangles with perimeter n whose side lengths are mutually coprime.
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1
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0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 7, 7, 0, 15, 0, 17, 9, 9, 11, 53, 11, 21, 37, 60, 26, 103, 13, 68, 28, 74, 49, 193, 34, 115, 106, 210, 74, 291, 76, 227, 97, 214, 107, 464, 132, 345, 205, 414, 117, 592, 198, 488, 223, 454, 214, 1037, 274, 591, 491
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OFFSET
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1,12
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LINKS
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FORMULA
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a(n) = Sum_{k=1..floor(n/3)} Sum_{i=k..floor((n-k)/2)} sign(floor((i+k)/(n-i-k+1))) * [gcd(i,k) * gcd(i,n-i-k) * gcd(k,n-i-k) = 1] * (n-i-k), where [] is the Iverson Bracket.
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MATHEMATICA
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Table[Sum[Sum[(n - i - k)*Floor[1/(GCD[i, k]*GCD[i, n - i - k]*GCD[k, n - i - k])]*Sign[Floor[(i + k)/(n - i - k + 1)]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 100}]
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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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