Number of points in Z^4 of norm <= n.

Terms

a(0) =1a(1) =9a(2) =89a(3) =425a(4) =1281a(5) =3121a(6) =6577a(7) =11833a(8) =20185a(9) =32633a(10) =49689a(11) =72465a(12) =102353a(13) =140945a(14) =190121a(15) =250553a(16) =323721a(17) =411913a(18) =519025a(19) =643441a(20) =789905a(21) =961721a(22) =1156217a(23) =1380729a(24) =1638241a(25) =1927297a(26) =2257281a(27) =2624417a(28) =3035033a(29) =3490601