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A307455
a(n) is the number of canonical polygons with n edges having exactly 1 line of reflection symmetry.
8
1, 0, 2, 2, 1, 7, 6, 28, 27, 107, 94, 488, 386, 2066, 1630, 8392, 6780, 34962, 28056, 147356, 117621, 622558, 500525, 2657666, 2149374
OFFSET
3,3
COMMENTS
For n even, the symmetry line passes through two opposite vertices, or cuts through two opposite edges. For n odd it passes through one vertex and cuts the opposite edge. That explains the even-odd irregularity in the sequence.
KEYWORD
nonn,more
AUTHOR
Lars Blomberg, Apr 09 2019
STATUS
approved