G.f. A(x) satisfies: A(x) = ( A(-x) + sqrt( A(-x)^2 + 64*x/A(-x) ) )/2.

Terms

a(0) =1a(1) =8a(2) =28a(3) =64a(4) =126a(5) =416a(6) =1680a(7) =5248a(8) =13973a(9) =53008a(10) =224092a(11) =768128a(12) =2298362a(13) =9091712a(14) =38646080a(15) =138919680a(16) =445239890a(17) =1791759736a(18) =7578341516a(19) =28075757440a(20) =94326701336a(21) =382678126688