a(n) = 250*n - 180.

Terms

a(0) =-180a(1) =70a(2) =320a(3) =570a(4) =820a(5) =1070a(6) =1320a(7) =1570a(8) =1820a(9) =2070a(10) =2320a(11) =2570a(12) =2820a(13) =3070a(14) =3320a(15) =3570a(16) =3820a(17) =4070a(18) =4320a(19) =4570a(20) =4820a(21) =5070a(22) =5320a(23) =5570a(24) =5820a(25) =6070a(26) =6320a(27) =6570a(28) =6820a(29) =7070