6^n mod 4^n.

Terms

a(0) =0a(1) =2a(2) =4a(3) =24a(4) =16a(5) =608a(6) =1600a(7) =1408a(8) =41216a(9) =116224a(10) =697344a(11) =2086912a(12) =12521472a(13) =41574400a(14) =249446400a(15) =959807488a(16) =3611361280a(17) =4488298496a(18) =61289529344a(19) =230298222592a(20) =282277707776