**Nimz ..** | Wednesday, March 09, 2005 - 09:52 pm Triangular Number--Definition: The sum of all whole numbers less than or equal to a given whole number. Formula: n(n+1)/2 "Tetrahedral" Number (Analogous Pyramid Number)--Definition: The sum of all triangular numbers less than or equal to a given triangular number. Formula: n(n+1)(n+2)/6 N-dimensional "Triangular" Number--Definition: The sum of all (N-1)-dimensional "Triangular" Numbers less than or equal to a given (N-1)-dimensional "Triangular" Number, where N=2 gives the standard Triangular Number. Formula: (N+n-1)!/((n-1)!N!) Okay, that was fun |