A229647 - OEIS

%I #13 Oct 22 2015 14:49:07

%S 1,4,28,232,2092,19864,195376,1971932,20303084,212400232,2251379688,

%T 24129199208,261067326544,2848016992032,31295785633532,

%U 346126420439512,3850363854970476,43057199315715676,483795646775017312,5459770924922887392

%N Cogrowth function of the group Baumslag-Solitar(5,5).

%C a(n) is the number of words of length 2n in the letters a,a^{-1},t,t^{-1} that equal the identity of the group BS(5,5)=<a,t | ta^5=a^5t>.

%H Murray Elder, <a href="/A229647/b229647.txt">Table of n, a(n) for n = 0..50</a>

%H M. Elder, A. Rechnitzer, E. J. Janse van Rensburg, T. Wong, <a href="http://arxiv.org/abs/1309.4184">The cogrowth series for BS(N,N) is D-finite</a>

%H <a href="/index/Gre#groups">Index entries for sequences related to groups</a>

%e For n=1 there are 4 words of length 2 equal to the identity: aa^{-1}, a^{-1}a, tt^{-1}, t^{-1}t.

%Y The cogrowth sequences for BS(N,N) for N = 1..10 are A002894, A229644, A229645, A229646, A229647, A229648, A229649, A229650, A229651, A229652.

%K nonn,walk

%O 0,2

%A _Murray Elder_, Sep 27 2013