Irregular triangle read by rows: T(n,k) is the number of n-permutations whose second-shortest cycle has length exactly k; n >= 0, 0 <= k <= max(0,n-1).

A349980

Irregular triangle read by rows: T(n,k) is the number of n-permutations whose second-shortest cycle has length exactly k; n >= 0, 0 <= k <= max(0,n-1).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =1a(6) =3a(7) =6a(8) =7a(9) =3a(10) =8a(11) =24a(12) =31a(13) =15a(14) =20a(15) =30a(16) =120a(17) =191a(18) =135a(19) =40a(20) =90a(21) =144a(22) =720a(23) =1331a(24) =945a(25) =280a(26) =420a(27) =504a(28) =840a(29) =5040

External references