a(n) = A026907(2*n, n-2).

Terms

a(0) =67a(1) =348a(2) =1495a(3) =6108a(4) =24501a(5) =97456a(6) =385900a(7) =1524066a(8) =6009720a(9) =23675882a(10) =93226503a(11) =367005692a(12) =1444728537a(13) =5687662392a(14) =22395051912a(15) =88199397642a(16) =347448657492