%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(n2)*A005568(1) + 2*A005566(n4)*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, A060898A060900.
%K nonn
%O 0,2
%A _David W. Wilson_, May 05 2001
