a(n) = floor(n/4)*floor((n+1)/4)*floor((n+2)/4)*floor((n+3)/4).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =4a(7) =8a(8) =16a(9) =24a(10) =36a(11) =54a(12) =81a(13) =108a(14) =144a(15) =192a(16) =256a(17) =320a(18) =400a(19) =500a(20) =625a(21) =750a(22) =900a(23) =1080a(24) =1296a(25) =1512a(26) =1764a(27) =2058a(28) =2401a(29) =2744