8 lines
571 B
Markdown
8 lines
571 B
Markdown
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This problem is very similar to the previous one. We iterate through all Pentagonal numbers (starting at P_144) and test the numbers if they are hexagonal.
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The test for hexagonal numbers is the same as in Problem-44, but we have to expand the iSquare function for int64 numbers ([20] is now 2^60 instead of 2^30).
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The major trick is that we only need to test for the hexagonal property. Because all hexagonal numbers are also Triangle numbers.
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Think about it, a Hexagon has six edges and a Triangle three, so every Hexagonal contains two triangles.
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`H_{n} == T_{2*n}`
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