Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k nonincreasing odd cycles (0<=k<=floor(n/3)). 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 1 nonincreasing odd cycle.

A186766

Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k nonincreasing odd cycles (0<=k<=floor(n/3)). 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 1 nonincreasing odd cycle.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =5a(4) =1a(5) =20a(6) =4a(7) =77a(8) =43a(9) =472a(10) =238a(11) =10a(12) =2585a(13) =2385a(14) =70a(15) =21968a(16) =16504a(17) =1848a(18) =157113a(19) =189695a(20) =15792a(21) =280a(22) =1724064a(23) =1591082a(24) =310854a(25) =2800a(26) =15229645a(27) =21449481a(28) =3100614a(29) =137060

External references