a(n) = 10^n mod 6^n.

Terms

a(0) =0a(1) =4a(2) =28a(3) =136a(4) =928a(5) =6688a(6) =20224a(7) =202240a(8) =902656a(9) =2308096a(10) =23080960a(11) =230809600a(12) =856907776a(13) =8569077760a(14) =7326613504a(15) =386722791424