a(n)=4*a(n-1)+6*a(n-2), n>1 ; a(0)=1, a(1)=6 .

Terms

a(0) =1a(1) =6a(2) =30a(3) =156a(4) =804a(5) =4152a(6) =21432a(7) =110640a(8) =571152a(9) =2948448a(10) =15220704a(11) =78573504a(12) =405618240a(13) =2093913984a(14) =10809365376a(15) =55800945408a(16) =288059973888