OFFSET
0,3
COMMENTS
Let M(s) denote the matrix
[s, -1]
[+1, 0]
in SL(2,Z). Then we count sequences of positive integers [s_1, ..., s_n] such that (Product_{k=1..n} M(s_k))^2 = -Identity.
This is Problem III in the Ovsienko article.
LINKS
Valentin Ovsienko, Partitions of unity in SL(2,Z), negative continued fractions, and dissections of polygons, Res. Math. Sci. 5, 21 (2018); arXiv:1710.02996 [math.CO], 2017-2018.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Michel Marcus, Oct 10 2017
STATUS
approved