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<p>Create Project Euler/242 - Odd Triplets (via create-page on MediaWiki MCP Server)</p> <p><b>New page</b></p><div>==Problem Statement==<br /> <br /> &#039;&#039;&#039;Odd Triplets&#039;&#039;&#039;<br /> <br /> Given the set {1,2,...,n}, we define f(n,k) as the number of its k-element subsets with an odd sum of elements. For example, f(5,3) = 4, since the set {1,2,3,4,5} has four 3-element subsets having an odd sum: {1,2,4}, {1,3,5}, {2,3,4} and {2,4,5}.<br /> <br /> When all three values n, k and f(n,k) are odd, we say that they make an odd-triplet [n,k,f(n,k)].<br /> <br /> There are exactly five odd-triplets with n ≤ 10, namely: [1,1,f(1,1) = 1], [5,1,f(5,1) = 3], [5,5,f(5,5) = 1], [9,1,f(9,1) = 5] and [9,9,f(9,9) = 1].<br /> <br /> How many odd-triplets are there with n ≤ 10^12?<br /> <br /> ==Flags==<br /> <br /> {{ProjectEulerFlag}}</div>

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