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A060897 Number of walks of length n on square lattice, starting at origin, staying in first and third quadrants. 5

%I

%S 1,4,12,44,144,528,1808,6676,23536,87568,315136,1180680,4314560,

%T 16263896,60138816,227899484,850600944,3238194560,12177384544,

%U 46542879384,176110444736,675431779856,2568878867200,9882068082112

%N Number of walks of length n on square lattice, starting at origin, staying in first and third quadrants.

%C Is there a formula analogous to the (conjectured) formula for A060900?

%C Could be broken into the number of walks that are constrained to a quadrant and the number that cross the origin. (I.e., 2*A005566(n) + 2*A005566(n-2)*A005568(1) + 2*A005566(n-4)*A005568(2) + ... + All terms that cross the origin twice + three times + ... + Cross floor(n/2) times.) - _Benjamin Phillabaum_, Mar 13 2011

%Y Cf. A005566, A005568, A001700, A060898-A060900.

%K nonn

%O 0,2

%A _David W. Wilson_, May 05 2001

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Last modified December 5 10:45 EST 2019. Contains 329751 sequences. (Running on oeis4.)