Number of ways a river can cross a road 2n times.
A077054
Number of ways a river can cross a road 2n times.
Terms
- a(0) =1a(1) =1a(2) =3a(3) =14a(4) =81a(5) =538a(6) =3926a(7) =30694a(8) =252939a(9) =2172830a(10) =19304190a(11) =176343390a(12) =1649008456a(13) =15730575554a(14) =152663683494
External references
- oeis: A077054