a(n)=(-4)*a(n-1)+8 with a(0)=1.

Terms

a(0) =1a(1) =4a(2) =-8a(3) =40a(4) =-152a(5) =616a(6) =-2456a(7) =9832a(8) =-39320a(9) =157288a(10) =-629144a(11) =2516584a(12) =-10066328a(13) =40265320a(14) =-161061272a(15) =644245096a(16) =-2576980376a(17) =10307921512a(18) =-41231686040a(19) =164926744168a(20) =-659706976664