31 Dec
2007
31 Dec
'07
12:54 p.m.
Can someone please point me to proofs without words for a) nth tetrahedral number = n(n+1)(n+2)/6 b) sum of the first n squares = n(n+1)(2n+1)/6 c) sum of the first n cubes = (sum of first n numbers)^2 = (T_n)^2 (T_n = nth triangular #) ? Thanks, Dan