generalization of http://www.jsoftware.com/papers/play132.htm, but explicit version:
involute=:3 : 0
t=.<./'M N'=.y
p=.,t{.|:(>:i.-N),:i.-M
d=.(+:t)$(,-)1,N
y$/:+/\p#d
)
involute 2 4
0 1 2 3
7 6 5 4
involute 3 5
0 1 2 3 4
11 12 13 14 5
10 9 8 7 6
involute 5 3
0 1 2
11 12 3
10 13 4
9 14 5
8 7 6
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