Number of -n..n arrays x(0..3) of 4 elements with zero sum and nonzero second differences.

Terms

a(0) =14a(1) =76a(2) =200a(3) =446a(4) =836a(5) =1368a(6) =2134a(7) =3140a(8) =4368a(9) =5942a(10) =7852a(11) =10064a(12) =12734a(13) =15836a(14) =19320a(15) =23374a(16) =27956a(17) =33000a(18) =38726a(19) =45076a(20) =51968a(21) =59654a(22) =68060a(23) =77088a(24) =87022a(25) =97772a(26) =109224a(27) =121694a(28) =135076a(29) =149240