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A137343
Number of elements of length n with respect to the natural metric in the special group of rational series over the finite field F_2 in two non-commuting variables.
1
1, 12, 1296, 505536, 679848192, 3248147205120, 57637071142391808, 3930578658351563587584, 1050888530707010579202637824, 1112792971262327168651248131637248
OFFSET
0,2
FORMULA
The reference contains a somewhat complicated formula.
CROSSREFS
Sequence in context: A239164 A209176 A351630 * A133461 A246981 A174745
KEYWORD
nonn
AUTHOR
Roland Bacher, Apr 08 2008
STATUS
approved