OFFSET
1,1
COMMENTS
Total number of walks as counted in A001411 that have a point of symmetry.
Note that for k > 4, we observe a(2k) < a(2k-1). This can be understood by considering interference between the parts at both sides of the point of symmetry (see illustration).
LINKS
Bert Dobbelaere, Table of n, a(n) for n = 1..60
Bert Dobbelaere, Illustration of initial terms
Bert Dobbelaere, C++ program
Brian Hayes, How to avoid yourself, American Scientist 86 (1998) 314-319.
FORMULA
MATHEMATICA
CROSSREFS
KEYWORD
nonn,walk
AUTHOR
Bert Dobbelaere, Jan 06 2019
STATUS
approved