a(n) = 2*a(n-2) + 4*a(n-3), with initial terms 0, 1, 1.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =6a(5) =8a(6) =20a(7) =40a(8) =72a(9) =160a(10) =304a(11) =608a(12) =1248a(13) =2432a(14) =4928a(15) =9856a(16) =19584a(17) =39424a(18) =78592a(19) =157184a(20) =314880a(21) =628736a(22) =1258496a(23) =2516992a(24) =5031936a(25) =10067968a(26) =20131840a(27) =40263680a(28) =80535552a(29) =161054720