a(n) = 13-n.

Terms

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