The negative integers.

Terms

a(0) =-1a(1) =-2a(2) =-3a(3) =-4a(4) =-5a(5) =-6a(6) =-7a(7) =-8a(8) =-9a(9) =-10a(10) =-11a(11) =-12a(12) =-13a(13) =-14a(14) =-15a(15) =-16a(16) =-17a(17) =-18a(18) =-19a(19) =-20a(20) =-21a(21) =-22a(22) =-23a(23) =-24a(24) =-25a(25) =-26a(26) =-27a(27) =-28a(28) =-29a(29) =-30