2nd differences are periodic.

Terms

a(0) =2a(1) =2a(2) =4a(3) =10a(4) =16a(5) =28a(6) =48a(7) =76a(8) =110a(9) =144a(10) =182a(11) =222a(12) =264a(13) =310a(14) =356a(15) =408a(16) =468a(17) =536a(18) =610a(19) =684a(20) =762a(21) =842a(22) =924a(23) =1010a(24) =1096a(25) =1188a(26) =1288a(27) =1396a(28) =1510a(29) =1624