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A284416
Number of self-avoiding planar walks of length 2n starting at (0,0), ending at (n,0), remaining in the first quadrant and using steps (0,1), (1,0), (1,1), (-1,1), and (1,-1) with the restriction that (0,1) is never used below the diagonal and (1,0) is never used above the diagonal.
3
1, 1, 1, 7, 17, 116, 536, 3732, 21609, 152225, 991680, 7142207, 49671146, 364955208, 2644449147, 19764753353, 147264417970, 1116423286310, 8488332597668, 65109780090520, 502742629038600, 3893865922507871, 30436537169536769, 237651376621912220
OFFSET
0,4
LINKS
Wikipedia, Lattice path
FORMULA
a(n) = A284414(n,2n).
CROSSREFS
Cf. A284414.
Sequence in context: A067185 A205989 A262474 * A063384 A165246 A266382
KEYWORD
nonn,walk
AUTHOR
Alois P. Heinz, Mar 26 2017
STATUS
approved