A108630 G.f.: (1+x-sqrt(1-2*x-7*x^2-8*x^3-4*x^4))/(2+2*x+2*x^2).

1, 1, 2, 6, 17, 54, 178, 606, 2116, 7533, 27242, 99799, 369583, 1381309, 5203599, 19737935, 75321337, 288968031, 1113893815, 4312073256, 16756934181, 65345024968, 255625711296, 1002888257745, 3945055462020, 15556613282788