a(n) = Sum_{k=0..n} binomial(4*k+2,k).

Terms

a(0) =1a(1) =7a(2) =52a(3) =416a(4) =3476a(5) =29810a(6) =260040a(7) =2295840a(8) =20452044a(9) =183463684a(10) =1654906657a(11) =14995689853a(12) =136395340953