a(n) = n-12.

Terms

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