Triangle T(n,k) read by rows: number of 12312-avoiding matchings on [2n] with exactly k crossings (n >= 1, 0 <= k <= n-1).
A108410
Triangle T(n,k) read by rows: number of 12312-avoiding matchings on [2n] with exactly k crossings (n >= 1, 0 <= k <= n-1).
Terms
- a(0) =1a(1) =2a(2) =1a(3) =5a(4) =5a(5) =2a(6) =14a(7) =21a(8) =15a(9) =5a(10) =42a(11) =84a(12) =84a(13) =49a(14) =14a(15) =132a(16) =330a(17) =420a(18) =336a(19) =168a(20) =42a(21) =429a(22) =1287a(23) =1980a(24) =1980a(25) =1350a(26) =594a(27) =132a(28) =1430a(29) =5005
External references
- oeis: A108410