P126
projecteuler.net

Cuboid Layers

ℹ️Published on Friday, 18th August 2006, 06:00 pm; Solved by 5376;
Difficulty rating: 55%

The minimum number of cubes to cover every visible face on a cuboid measuring $3 \times 2 \times 1$ is twenty-two.


If we then add a second layer to this solid it would require forty-six cubes to cover every visible face, the third layer would require seventy-eight cubes, and the fourth layer would require one-hundred and eighteen cubes to cover every visible face.

However, the first layer on a cuboid measuring $5 \times 1 \times 1$ also requires twenty-two cubes; similarly the first layer on cuboids measuring $5 \times 3 \times 1$, $7 \times 2 \times 1$, and $11 \times 1 \times 1$ all contain forty-six cubes.

We shall define $C(n)$ to represent the number of cuboids that contain $n$ cubes in one of its layers. So $C(22) = 2$, $C(46) = 4$, $C(78) = 5$, and $C(118) = 8$.

It turns out that $154$ is the least value of $n$ for which $C(n) = 10$.

Find the least value of $n$ for which $C(n) = 1000$.



Soluzione

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