A049780 Array T read by diagonals: T(m,n)=m+1 + m+2 + ... + m+n = (n/2)(n+2m+1).

0, 1, 0, 3, 2, 0, 6, 5, 3, 0, 10, 9, 7, 4, 0, 15, 14, 12, 9, 5, 0, 21, 20, 18, 15, 11, 6, 0, 28, 27, 25, 22, 18, 13, 7, 0, 36, 35, 33, 30, 26, 21, 15, 8, 0, 45, 44, 42, 39, 35, 30, 24, 17, 9, 0, 55, 54, 52, 49, 45, 40, 34, 27, 19, 10, 0, 66, 65, 63