A138275 Central terms of triangle A138271.
1, 2, 18, 268, 5320, 129474, 3700550, 121016160, 4448701704, 181463572394, 8130511993010, 396880976034092, 20963000461338000, 1191187898025406514, 72455444438093714542, 4697146562744837487104, 323299667265950287087968
Offset: 0