a(n) = Lucas(4*n + 3).

Terms

a(0) =4a(1) =29a(2) =199a(3) =1364a(4) =9349a(5) =64079a(6) =439204a(7) =3010349a(8) =20633239a(9) =141422324a(10) =969323029a(11) =6643838879a(12) =45537549124a(13) =312119004989