Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k increasing odd cycles (0<=k<=n). A cycle (b(1), b(2), ...) is said to be increasing if, when written with its smallest element in the first position, it satisfies b(1)<b(2)<b(3)<... . A cycle is said to be odd if it has an odd number of entries. For example, the permutation (152)(347)(6)(8) has 3 increasing odd cycles.
A186761
Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k increasing odd cycles (0<=k<=n). A cycle (b(1), b(2), ...) is said to be increasing if, when written with its smallest element in the first position, it satisfies b(1)<b(2)<b(3)<... . A cycle is said to be odd if it has an odd number of entries. For example, the permutation (152)(347)(6)(8) has 3 increasing odd cycles.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =0a(5) =1a(6) =1a(7) =4a(8) =0a(9) =1a(10) =9a(11) =4a(12) =10a(13) =0a(14) =1a(15) =33a(16) =56a(17) =10a(18) =20a(19) =0a(20) =1a(21) =235a(22) =218a(23) =211a(24) =20a(25) =35a(26) =0a(27) =1a(28) =1517a(29) =1982
External references
- oeis: A186761