a(1) = 1, then multiply, add and subtract 2, 3, 4; 5, 6, 7; ... in that order.

Terms

a(0) =1a(1) =2a(2) =5a(3) =1a(4) =5a(5) =11a(6) =4a(7) =32a(8) =41a(9) =31a(10) =341a(11) =353a(12) =340a(13) =4760a(14) =4775a(15) =4759a(16) =80903a(17) =80921a(18) =80902a(19) =1618040a(20) =1618061a(21) =1618039a(22) =37214897a(23) =37214921a(24) =37214896a(25) =967587296a(26) =967587323a(27) =967587295a(28) =28060031555a(29) =28060031585