Number of paths from (0,0) to (n,n) using only steps North, Northeast and East (i.e., steps E(1,0), D(1,1), and N(0,1)) that do not cross y=x "vertically".

A268208

Number of paths from (0,0) to (n,n) using only steps North, Northeast and East (i.e., steps E(1,0), D(1,1), and N(0,1)) that do not cross y=x "vertically".

Terms

    a(0) =1a(1) =3a(2) =12a(3) =52a(4) =236a(5) =1108a(6) =5340a(7) =26276a(8) =131484a(9) =667108a(10) =3424108a(11) =17748564a(12) =92776716a(13) =488527284a(14) =2588907708a(15) =13797337668a(16) =73901315644a(17) =397609958596

External references