There are 1 cube in the first layer, 3 cubes in the second layer, and 6 cubes in the third layer How many cubes are there in layer N? Expressed by the formula with n
1,3,6,10,15,.
The expression is: (1 + n) * n / 2
The n-th layer has: (1 + n) * n / 2 cubes
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