a(n) = 27 - n.

Terms

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