a(0)=1, a(1)=4, a(n) = 12*a(n-2) - a(n-1).

Terms

a(0) =1a(1) =4a(2) =8a(3) =40a(4) =56a(5) =424a(6) =248a(7) =4840a(8) =-1864a(9) =59944a(10) =-82312a(11) =801640a(12) =-1789384a(13) =11409064a(14) =-32881672a(15) =169790440a(16) =-564370504a(17) =2601855784a(18) =-9374301832a(19) =40596571240a(20) =-153088193224a(21) =640247048104