Number of ways a loop can cross three roads meeting in a Y n times. The loop must touch the southwest sector.

A078104

Number of ways a loop can cross three roads meeting in a Y n times. The loop must touch the southwest sector.

Terms

    a(0) =1a(1) =0a(2) =2a(3) =1a(4) =7a(5) =6a(6) =37a(7) =42a(8) =237a(9) =320a(10) =1715a(11) =2610a(12) =13478a(13) =22404a(14) =112480a(15) =200158a(16) =982561a(17) =1846314a(18) =8897089a(19) =17481864

External references