a(n) = n-27.

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