Number of n-digit even numbers.

Terms

a(0) =5a(1) =45a(2) =450a(3) =4500a(4) =45000a(5) =450000a(6) =4500000a(7) =45000000a(8) =450000000a(9) =4500000000a(10) =45000000000a(11) =450000000000