Number of permutations of 2 indistinguishable copies of 1..n with exactly 4 adjacent element pairs in decreasing order.
A151626
Number of permutations of 2 indistinguishable copies of 1..n with exactly 4 adjacent element pairs in decreasing order.
Terms
- a(0) =0a(1) =0a(2) =1a(3) =603a(4) =47290a(5) =1822014a(6) =49258935a(7) =1086859301a(8) =21147576440a(9) =379269758400
External references
- oeis: A151626