a(n) = Sum_{k=0..floor(n/2)} C(n,2k)*Pell(k).

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =8a(5) =20a(6) =50a(7) =126a(8) =320a(9) =816a(10) =2084a(11) =5324a(12) =13600a(13) =34736a(14) =88712a(15) =226552a(16) =578560a(17) =1477504a(18) =3773200a(19) =9635888a(20) =24607872a(21) =62842944a(22) =160486688a(23) =409846752a(24) =1046656000a(25) =2672922880a(26) =6826040896a(27) =17432165568a(28) =44517810688a(29) =113688426240