a(n) = 2*{0,a(n-2),0} + 2*{-1/2,a(n-1)}+2*{a(n-1),-1/2}.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =6a(5) =1a(6) =1a(7) =16a(8) =16a(9) =1a(10) =1a(11) =36a(12) =76a(13) =36a(14) =1a(15) =1a(16) =76a(17) =256a(18) =256a(19) =76a(20) =1a(21) =1a(22) =156a(23) =736a(24) =1176a(25) =736a(26) =156a(27) =1a(28) =1a(29) =316