

A293492


a(n) is the number of sequences (s_1, ..., s_n) of positive integers such that Product_{k=1..n} [s_k, 1/1, 0]^2 = [1, 0/0, 1].


0




OFFSET

0,3


COMMENTS

Let M(s) denote the matrix
[s, 1]
[+1, 0]
in SL(2,Z). The we count sequences of positive integers [s_1, ..., s_n] such that Prod_{k=1..n} M(s_k)^2 =  Identity.
This is Problem III in the Ovsienko article.


LINKS

Table of n, a(n) for n=0..6.
Valentin Ovsienko, Partitions of unity in SL(2,Z), negative continued fractions, and dissections of polygons, arXiv:1710.02996 [math.CO], 2017.


CROSSREFS

Sequence in context: A150158 A034010 A135588 * A150159 A150160 A150161
Adjacent sequences: A293489 A293490 A293491 * A293493 A293494 A293495


KEYWORD

nonn,more


AUTHOR

Michel Marcus, Oct 10 2017


STATUS

approved



