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Tetrahedral numbers
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(Redirected from Triangular pyramidal numbers)
n 

Tn = n∑ i = 1
ti 
i 
Tetrahedral numbers can also be obtained from binomial coefficients (which means that they can be looked up in Pascal’s triangle)

Tn = ( ^{n + 3}_{3} ) − ( ^{n + 2}_{2} ) = ( ^{n + 2}_{3} ) =
,n ( 3 ) 3!
n (k ) 
A000292 Tetrahedral (or triangular pyramidal) numbers:
a (n) = ( ^{n + 2}_{3} ) =

 {0, 1, 4, 10, 20, 35, 56, 84, 120, 165, 220, 286, 364, 455, 560, 680, 816, 969, 1140, 1330, 1540, 1771, 2024, 2300, 2600, 2925, 3276, 3654, 4060, 4495, 4960, 5456, 5984, 6545, 7140, ...}
See also
 4faced Platonic numbers.
 3dimensional simplicial polytopic numbers.