one-sided pentominoes: Torsten Sillke, May 1993 update 1999-01-15: the odd prime L5 rectangles update 1999-03-20: the odd prime Y5 rectangles update 1999-04-14: the odd prime P5 rectangles There are three pentominoes, which tile rectangles and are handed. These are: L, P, and Y. prime rectangles odd who and when +----------------------------------+-----+------------------------------ L5 | 2x5, 13x55, 15x39, 17x35, 19x25 | yes | Michael Reid [until may 1998] Y5 | 5x10 | no | Yuri Aksyonov 1999-03-20 P5 | 2x5 | no | Michael Reid one-sided tetrominoes: The handed L4 is long known to have odd rectangles. (D. A. Klarner, AMM 70:7 (Sep. 1963) 760-61 E1543). The L5 rectangles: The smallest odd rectangle with right handed L5 is 19x25: +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | | | | | | | | + +--+--+--+ + +--+--+--+ + +--+--+--+ + +--+ +--+ | | | | | | | | | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + + + + | | | | | | | | | | | + +--+--+--+ + +--+--+--+ + +--+--+--+ + + + + + | | | | | | | | | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+ + | | | | | | | | | + +--+--+--+ + +--+--+--+ + +--+--+--+ +--+--+--+--+ | | | | | | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + | | | | | | | | | | + +--+ +--+ +--+ +--+ +--+--+--+ + +--+--+--+ +--+ | | | | | | | | | | | | | | + + + + + + + + +--+--+--+--+--+--+--+--+--+--+ + | | | | | | | | | | | | | + + + + + + + +--+--+--+--+ + +--+--+--+--+ + + | | | | | | | | | | | | | | +--+ +--+ +--+ +--+--+--+--+ + + +--+--+--+ +--+ + | | | | | | | | | | | | +--+--+--+--+--+--+--+--+--+ +--+ + + +--+ +--+--+--+ | | | | | | | | | | | + +--+--+--+ + +--+ +--+--+--+--+--+ + +--+--+--+--+ | | | | | | | | | | | +--+--+--+--+--+ + + + +--+--+--+ + +--+--+--+--+ + | | | | | | | | | | | + +--+--+--+ + + + +--+--+--+--+--+--+--+--+--+ + + | | | | | | | | | | | +--+--+--+--+--+--+ +--+--+--+--+ + +--+--+--+ +--+ + | | | | | | | | | + +--+--+--+ +--+--+--+--+--+ +--+--+--+--+--+--+--+--+ | | | | | | | | | | +--+--+--+--+--+ +--+--+--+ +--+ +--+ +--+ +--+ +--+ | | | | | | | | | | | | | | + +--+--+--+ +--+--+--+--+--+ + + + + + + + + + | | | | | | | | | | | | | | +--+--+--+--+--+ +--+--+--+ + + + + + + + + + + | | | | | | | | | | | | | | + +--+--+--+ +--+--+--+--+--+ +--+ +--+ +--+ +--+ + | | | | | | | | | | +--+--+--+--+--+ +--+ +--+--+--+--+--+--+--+--+--+--+--+ | | | | | | | | | | | + +--+--+--+ + + + + + +--+--+--+ + +--+--+--+ + | | | | | | | | | | | +--+--+--+--+--+ + + + +--+--+--+--+--+--+--+--+--+--+ | | | | | | | | | | | + +--+--+--+ +--+ +--+ + +--+--+--+ + +--+--+--+ + | | | | | | | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ The tiling group of L5: The left-L5 is member of the right-L5 tiling group (Michael Reid) This property gave hope to find an odd right-L5 rectangle. a d baaaa ddd-- bbbb ddd- cccc ddd- c - aab --- abbb ---- abbb ---c abbb cccc which gives the other orientation of L! The tiling group of P5: Theorem P5(right) [Michael Reid]: x * y^5 * x^-1 * y^-5 is no relation of the group < x, y | x^3 * y^2 * x^-2 * y^-1 * x^-1 * y^-1, y^3 * x^-2 * y^-2 * x * y^-1 * x, x^-3 * y^-2 * x^2 * y * x * y, y^-3 * x^2 * y^2 * x^-1 * y * x^-1 > Michael Reid was able to settle the one-sided P pentomino. It does not tile any odd rectangle, as expected. Here's a homomorphism to S_80: (The computations have been done by GAP.) gap> x := ( 1, 4, 5, 8, 9, 2, 3, 6, 7,10)(11,24,35,62,71,12,23,36,61,72) > (13,26,41,56,63,14,25,42,55,64)(15,21,48,49,65,16,22,47,50,66) > (17,30,37,60,67,18,29,38,59,68)(19,27,46,53,69,20,28,45,54,70) > (31,44,51,73,78,32,43,52,74,77)(33,40,57,75,80,34,39,58,76,79);; gap> y := ( 1,21,62,12,46)( 2,27,61,18,45,63,22,60,11,48)( 3,39,67,32,56) > ( 4,43,68,34,55,13,40,71,31,10)( 6,58,78,41,65,25,51,79, 8,70) > ( 5,52,77, 7,66)( 9,14,44,72,33)(15,38,75,30,53,20,35,74,23,50) > (16,36,76,24,54)(17,47,64,28,59)(19,37,73,29,49)(26,57,80,42,69);; gap> x^3 * y^2 * x^-2 * y^-1 * x^-1 * y^-1; () gap> y^3 * x^-2 * y^-2 * x * y^-1 * x; () gap> x^-3 * y^-2 * x^2 * y * x * y; () gap> y^-3 * x^2 * y^2 * x^-1 * y * x^-1; () gap> x * y^5 * x^-1 * y^-5; ( 1,64)( 2,63)( 3,14)( 4,13)( 5,26)( 6,25)( 7,42)( 8,41)( 9,56)(10,55)(11,18) (12,17)(15,20)(16,19)(21,28)(22,27)(23,30)(24,29)(31,34)(32,33)(35,38)(36,37) (39,44)(40,43)(45,48)(46,47)(49,54)(50,53)(51,58)(52,57)(59,62)(60,61)(65,70) (66,69)(67,72)(68,71)(73,76)(74,75)(77,80)(78,79) gap> References: - Yuri Aksyonov Handed Y-pentomino problem is solved, email from 1999-03-06 - David A. Klarner Solution to Problem E1543, AMM 70:7 (Sep. 1963) 760-61 (prime rectangles for L4 and "one-sided" L4.) - Michael Reid There are odd "one-sided" L pentominoes prime rectangles, email from 1999-01-15 - Michael Reid G hexomino [and handed P pentomino solved], email from 1999-04-14