Number of -n..n arrays of 4 elements with first, second and third differences also in -n..n.

Terms

a(0) =19a(1) =127a(2) =475a(3) =1279a(4) =2833a(5) =5509a(6) =9739a(7) =16039a(8) =25003a(9) =37279a(10) =53605a(11) =74797a(12) =101719a(13) =135331a(14) =176671a(15) =226819a(16) =286957a(17) =358345a(18) =442279a(19) =540163a(20) =653479a(21) =783739a(22) =932569a(23) =1101673a(24) =1292779a(25) =1507735a(26) =1748467a(27) =2016919a(28) =2315161a(29) =2645341