a(n) is the final nonzero digit of n!.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =4a(5) =2a(6) =2a(7) =4a(8) =2a(9) =8a(10) =8a(11) =8a(12) =6a(13) =8a(14) =2a(15) =8a(16) =8a(17) =6a(18) =8a(19) =2a(20) =4a(21) =4a(22) =8a(23) =4a(24) =6a(25) =4a(26) =4a(27) =8a(28) =4a(29) =6