Irregular triangle read by rows: T(n,k) is the number of permutations in S_n having k stretching pairs.
A216120
Irregular triangle read by rows: T(n,k) is the number of permutations in S_n having k stretching pairs.
Terms
- a(0) =1a(1) =2a(2) =6a(3) =22a(4) =2a(5) =94a(6) =22a(7) =4a(8) =462a(9) =172a(10) =72a(11) =12a(12) =2a(13) =2582a(14) =1244a(15) =824a(16) =276a(17) =94a(18) =16a(19) =4a(20) =16214a(21) =9126a(22) =8016a(23) =3996a(24) =1990a(25) =660a(26) =248a(27) =56a(28) =12a(29) =2
External references
- oeis: A216120