Number of permutations of 2 indistinguishable copies of 1..n with exactly 2 adjacent element pairs in decreasing order.
A151624
Number of permutations of 2 indistinguishable copies of 1..n with exactly 2 adjacent element pairs in decreasing order.
Terms
- a(0) =0a(1) =1a(2) =48a(3) =603a(4) =5158a(5) =37257a(6) =247236a(7) =1568215a(8) =9703890a(9) =59226357a(10) =358722928a(11) =2163496611a(12) =13017647646a(13) =78225458401a(14) =469740168924
External references
- oeis: A151624