Number of permutations of 2 indistinguishable copies of 1..n with exactly 3 adjacent element pairs in decreasing order.
A151625
Number of permutations of 2 indistinguishable copies of 1..n with exactly 3 adjacent element pairs in decreasing order.
Terms
- a(0) =0a(1) =0a(2) =20a(3) =1168a(4) =27664a(5) =450048a(6) =6030140a(7) =72338144a(8) =811888600a(9) =8742609264a(10) =91700484132a(11) =945739871600
External references
- oeis: A151625