A027161 T(2n-1,n-1), T given by A027157.
2, 6, 40, 152, 1088, 4416, 32384, 135552, 1006592, 4289536, 32100352, 138407936, 1041203200, 4526702592, 34182430720, 149528084480, 1132376883200, 4977103994880, 37776580935680, 166668216041472, 1267318675996672
Offset: 1