n 1000000
Min 14.0
Max 170.0
Mean 41.47805800000006
Stddev 12.25866113503174

largest rectangular region in z340 that covers no repeating bigram:  5x10 (50 positions)

positions	count
14	7
15	31
16	161
17	181
18	1403
19	8
20	3891
21	5023
22	4175
24	26545
25	11161
26	9177
27	17147
28	37734
30	75745
32	45105
33	29665
34	32642
35	41060
36	112473
38	1131
39	24894
40	81125
42	67415
44	28308
45	55158
48	54117
49	15478
50	24637
51	20686
52	16130
54	18467
55	15197
56	29226
57	742
60	28628
63	8506
64	6387
65	5473
66	6599
68	5074
70	7623
72	8095
75	2062
76	194
77	2253
78	1750
80	2274
81	937
84	2005
85	1080
88	836
90	1298
91	578
95	37
96	463
98	270
99	301
100	157
102	173
104	148
105	124
108	142
110	117
112	70
114	10
117	42
119	50
120	82}
121	18
126	28
128	9
130	13
132	9
135	3
136	11
140	9
143	1
144	5
150	2
153	1
154	2
160	1
162	1
165	1
168	1
170	2

219040 of 1000000 shuffles (22%) have rectangular regions of size 50 or higher.