Number of North-East lattice paths from (0,0) to (n,n) that cross the diagonal y = x horizontally exactly four times.

A268447

Number of North-East lattice paths from (0,0) to (n,n) that cross the diagonal y = x horizontally exactly four times.

Terms

    a(0) =1a(1) =18a(2) =189a(3) =1518a(4) =10350a(5) =63180a(6) =356265a(7) =1893294a(8) =9612108a(9) =47071640a(10) =223926516a(11) =1040310648a(12) =4739192952a(13) =21238169904a(14) =93865125915a(15) =409972529754

External references