Number of zero-sum -n..n arrays of 6 elements with adjacent element differences also in -n..n.

Terms

a(0) =33a(1) =387a(2) =2003a(3) =6963a(4) =18841a(5) =43293a(6) =88301a(7) =164873a(8) =287151a(9) =473293a(10) =745359a(11) =1130441a(12) =1660283a(13) =2372685a(14) =3310839a(15) =4525059a(16) =6071723a(17) =8015439a(18) =10427561a(19) =13388757a(20) =16987109a(21) =21321159a(22) =26497455a(23) =32634197a(24) =39858185a(25) =48309035a(26) =58135563a(27) =69500619a(28) =82576757a(29) =97551845