Triangle T(n,k) read by rows: number of k-lists (ordered k-sets) of disjoint 2-subsets of an n-set, n>1, 0<k<=floor(n/2).

A157018

Triangle T(n,k) read by rows: number of k-lists (ordered k-sets) of disjoint 2-subsets of an n-set, n>1, 0<k<=floor(n/2).

Terms

    a(0) =1a(1) =3a(2) =6a(3) =6a(4) =10a(5) =30a(6) =15a(7) =90a(8) =90a(9) =21a(10) =210a(11) =630a(12) =28a(13) =420a(14) =2520a(15) =2520a(16) =36a(17) =756a(18) =7560a(19) =22680a(20) =45a(21) =1260a(22) =18900a(23) =113400a(24) =113400a(25) =55a(26) =1980a(27) =41580a(28) =415800a(29) =1247400

External references