a(n) = 12-n.

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