a(n) = n - 1.

Terms

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