Partial sums of the even Lucas numbers (A014448).

Terms

a(0) =2a(1) =6a(2) =24a(3) =100a(4) =422a(5) =1786a(6) =7564a(7) =32040a(8) =135722a(9) =574926a(10) =2435424a(11) =10316620a(12) =43701902a(13) =185124226a(14) =784198804a(15) =3321919440a(16) =14071876562a(17) =59609425686a(18) =252509579304