A229646 Cogrowth function of the group Baumslag-Solitar(4,4).

1, 4, 28, 232, 2092, 19884, 196096, 1988424, 20611116, 217526524, 2330681348, 25296553088, 277653104800, 3077568629256, 34410056828392, 387725845018512, 4399241841920428, 50228061806093020, 576729989899675348

Offset

0,2

Comments

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(4,4)=<a,t | ta^4=a^4t>.

Links

Murray Elder, Table of n, a(n) for n = 0..50

M. Elder, A. Rechnitzer, E. J. Janse van Rensburg, T. Wong, The cogrowth series for BS(N,N) is D-finite

Index entries for sequences related to groups

Example

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

Crossrefs

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

Sequence in context: A359705 A229648 A229647 * A229645 A359798 A307468

Adjacent sequences: A229643 A229644 A229645 * A229647 A229648 A229649

Keyword

nonn,walk

Author

Murray Elder, Sep 27 2013

Status

approved