Number of -n..n arrays x(0..3) of 4 elements with zero sum and no two neighbors equal.

Terms

a(0) =8a(1) =52a(2) =168a(3) =380a(4) =724a(5) =1236a(6) =1940a(7) =2872a(8) =4068a(9) =5552a(10) =7360a(11) =9528a(12) =12080a(13) =15052a(14) =18480a(15) =22388a(16) =26812a(17) =31788a(18) =37340a(19) =43504a(20) =50316a(21) =57800a(22) =65992a(23) =74928a(24) =84632a(25) =95140a(26) =106488a(27) =118700a(28) =131812a(29) =145860