a(n) = ((-9*n + 82)*10^n - 1)/81.

Terms

a(0) =1a(1) =9a(2) =79a(3) =679a(4) =5679a(5) =45679a(6) =345679a(7) =2345679a(8) =12345679a(9) =12345679a(10) =-987654321a(11) =-20987654321a(12) =-320987654321