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A229649
Cogrowth function of the group Baumslag-Solitar(7,7).
10
1, 4, 28, 232, 2092, 19864, 195352, 1970896, 20275692, 211825564, 2240852928, 23952708696, 258285519688, 2806105225928, 30685515254240, 337472968923532, 3730218568024236, 41417273400310152, 461722437389957236, 5166105817092273412
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(7,7)=<a,t | ta^7=a^7t>.
LINKS
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: A229652 A229651 A229650 * A359705 A229648 A229647
KEYWORD
nonn,walk
AUTHOR
Murray Elder, Sep 27 2013
STATUS
approved