What is Tetrahedral Number?
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The {n}th tetrahedral number is the sum of the first n Triangular numbers. Triangular numbers are the sum of the first n integers (1, 3, 6, 10, 15, etc.), and taking the sum of the triangular numbers results in the tetrahedral numbers (1, 4, 10, 20, 35, etc.)
The fifth tetrahedral number is the sum of the first five triangular numbers. The first five triangular numbers are 1, 3=1+2, 6=1+2+3, 10=1+2+3+4, and 15=1+2+3+4+5, so the sum of these numbers is 1+3+6+10+15= 35.
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The day Yello takes me out for my birthday to Chilis when she gets her first pay check. and then we rent a movie and watch it!! The date..
