a(0)=1, a(1)=4, a(n)=8a(n-1)-13a(n-2), n>=2.

Terms

a(0) =1a(1) =4a(2) =19a(3) =100a(4) =553a(5) =3124a(6) =17803a(7) =101812a(8) =583057a(9) =3340900a(10) =19147459a(11) =109747972a(12) =629066809a(13) =3605810836a(14) =20668618171a(15) =118473404500a(16) =679095199777