A047125 T(n,n-3), array T as in A047120.
1, 2, 6, 28, 120, 501, 2020, 8062, 31992, 126556, 499478, 1968504, 7751812, 30513489, 120090702, 472636988, 1860354732, 7323975621, 28840527086, 113600162826, 447592682400, 1764087889221, 6954932056860, 27428450072466
Offset: 3