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A060897 Number of walks of length n on square lattice, starting at origin, staying in first and third quadrants. 5
1, 4, 12, 44, 144, 528, 1808, 6676, 23536, 87568, 315136, 1180680, 4314560, 16263896, 60138816, 227899484, 850600944, 3238194560, 12177384544, 46542879384, 176110444736, 675431779856, 2568878867200, 9882068082112 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

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

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

LINKS

Table of n, a(n) for n=0..23.

CROSSREFS

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

Sequence in context: A259223 A167402 A320643 * A005190 A149360 A149361

Adjacent sequences:  A060894 A060895 A060896 * A060898 A060899 A060900

KEYWORD

nonn

AUTHOR

David W. Wilson, May 05 2001

STATUS

approved

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Last modified November 15 01:25 EST 2019. Contains 329143 sequences. (Running on oeis4.)