A049728 a(n)=T(n,n), array T as in A049723.
1, 6, 15, 35, 56, 88, 121, 162, 214, 267, 331, 396, 461, 553, 634, 734, 827, 931, 1040, 1153, 1289, 1414, 1554, 1691, 1832, 2004, 2161, 2329, 2502, 2678, 2867, 3056, 3264, 3469, 3681, 3902, 4107, 4351, 4584, 4840, 5081, 5330
Offset: 0