A047144 T(n,n-2), array T as in A047140.
1, 4, 13, 42, 148, 540, 1945, 6994, 25784, 96564, 361560, 1353608, 5113044, 19462184, 74227737, 283335006, 1085696746, 4176869836, 16100775648, 62132631186, 240258482330, 931152718588, 3614359486290, 14044139747816
Offset: 2