Triangle read by rows: a(n,k) = number of permutations in S_n which avoid the pattern 123 and have exactly k descents.
A166073
Triangle read by rows: a(n,k) = number of permutations in S_n which avoid the pattern 123 and have exactly k descents.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =0a(5) =4a(6) =1a(7) =0a(8) =2a(9) =11a(10) =1a(11) =0a(12) =0a(13) =15a(14) =26a(15) =1a(16) =0a(17) =0a(18) =5a(19) =69a(20) =57a(21) =1a(22) =0a(23) =0a(24) =0a(25) =56a(26) =252a(27) =120a(28) =1a(29) =0
External references
- oeis: A166073