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 A337901 The number of walks of length 2n+1 on the square lattice that start from the origin (0,0) and end at the vertex (3,0). 3
 1, 25, 441, 7056, 108900, 1656369, 25050025, 378224704, 5712638724, 86394844900, 1308887012356, 19868414760000, 302198588499600, 4605510959127225, 70321771565375625, 1075697380745222400, 16483023079048102500, 252980753801047064100, 3888662839165553120100 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..19. FORMULA a(n) = [A002054(n)]^2. G.f.: x*4F3(2,2,5/2,5/2; 1,4,4; 16*x). D-finite with recurrence (n+2)^2*(n-1)^2*a(n) -4*n^2*(2*n+1)^2*a(n-1)=0. CROSSREFS Cf. A002894 (end at (0,0)), A060150 (end at (1,0)), A135389 (end at (1,1)), A337900 (at (2,0)), A337902 (at(2,1)) Sequence in context: A018207 A362428 A264382 * A260854 A001714 A016633 Adjacent sequences: A337898 A337899 A337900 * A337902 A337903 A337904 KEYWORD nonn,easy,walk AUTHOR R. J. Mathar, Sep 29 2020 STATUS approved

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Last modified June 4 13:02 EDT 2023. Contains 363128 sequences. (Running on oeis4.)