a(n) = 10^(n-1) - 1 + n*floor(9*10^(n-1)/(n+1)).
A093852
a(n) = 10^(n-1) - 1 + n*floor(9*10^(n-1)/(n+1)).
Terms
- a(0) =4a(1) =69a(2) =774a(3) =8199a(4) =84999a(5) =871425a(6) =8874999a(7) =89999999a(8) =909999999a(9) =9181818179a(10) =92499999999a(11) =930769230759
External references
- oeis: A093852