Number of idempotent 4X4 0..n matrices.

Terms

a(0) =452a(1) =2052a(2) =5584a(3) =12476a(4) =23568a(5) =41668a(6) =67136a(7) =104112a(8) =153604a(9) =219728a(10) =303468a(11) =412720a(12) =545012a(13) =709272a(14) =907828a(15) =1146704a(16) =1426212a(17) =1759348a(18) =2142176a(19) =2590236a(20) =3101848a(21) =3686444a(22) =4346808a(23) =5102188a(24) =5942936