As a reply to the question of existance of 16x16 windoku's by Hajime here:
http://forum.enjoysudoku.com/giant-sudokus-t39758-75.html
...A.G.6C.D.3....3.E........F.D....G..3485..C...4C6..........AB8.....3.2G.A.....5...G......F...C..A....5D....3..G.3.6.4..C.9.E.73.2.4.A..G.8.B.D..5....F3....4..A...C......5...3.....5.3A.C.....6BC..........721...3..C8BE..4....9.7........E.3....F.6.15.7.A...
....E8.3G.C2......A1........D9...3....7F5E....B..F.5........2.A.C....EA..13....D1...C......8...A..7.5......C.2..F.3....GB....1.CA.G....E9....7.3..F.B......6.A..9...3......A...F3....C9..G8....1.2.9........7.4..G....45C2....F...C3........18......G2.76.49....
...J.P.FL.M.C....C.N........O.M....P..CDHE..L...DLF..........JKH.....C.BP.J.....E...P......O...L..J....EM....C..P.C.F.D..L.I.N.GC.B.D.J..P.H.K.M..E....OC....D..J...L......E...C.....E.CJ.L.....FKL..........GBA...C..LHKN..D....I.G........N.C....O.F.AE.G.J... ED=2.0/1.2/1.2
....NH.CP.LB......JA........MI...C....GOEN....K..O.E........B.J.L....NJ..AC....MA...L......H...J..G.E......L.B..O.C....PK....A.LJ.P....NI....G.C..O.K......F.J..I...C......J...OC....LI..PH....A.B.I........G.D..P....DELB....O...LC........AH......PB.GF.DI.... ED=2.8/1.2/1.2