Number of zero-sum -2..2 arrays of n elements with first through fourth differences also in -2..2.

Terms

a(0) =1a(1) =3a(2) =5a(3) =15a(4) =21a(5) =37a(6) =39a(7) =65a(8) =107a(9) =183a(10) =313a(11) =527a(12) =853a(13) =1459a(14) =2455a(15) =4167a(16) =7051a(17) =11857a(18) =20009a(19) =33993a(20) =57671a(21) =98267a(22) =167457a(23) =285197a(24) =487513a(25) =833647a(26) =1427739a(27) =2448037a(28) =4197785a(29) =7202371