A038744 T(2n,n), array T as in A038738.
1, 5, 30, 188, 1201, 7756, 50439, 329625, 2161974, 14220038, 93740152, 619083041, 4094863900, 27120465023, 179822255181
Offset: 0
Formula
G.f.: (g-1)/((3*g-1)*(g^2-3*g+1)) where g*(1-g)^2 = x. - Mark van Hoeij, Nov 10 2011