a(n) = n-19.

Terms

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