Number of -n..n arrays of 4 elements with adjacent element differences also in -n..n.

Terms

a(0) =41a(1) =295a(2) =1111a(3) =3011a(4) =6691a(5) =13021a(6) =23045a(7) =37981a(8) =59221a(9) =88331a(10) =127051a(11) =177295a(12) =241151a(13) =320881a(14) =418921a(15) =537881a(16) =680545a(17) =849871a(18) =1048991a(19) =1281211a(20) =1550011a(21) =1859045a(22) =2212141a(23) =2613301a(24) =3066701a(25) =3576691a(26) =4147795a(27) =4784711a(28) =5492311a(29) =6275641