Number of permutations of 1..n with no adjacent pair summing to n+1.
A173841
Number of permutations of 1..n with no adjacent pair summing to n+1.
Terms
- a(0) =1a(1) =1a(2) =0a(3) =2a(4) =8a(5) =48a(6) =240a(7) =1968a(8) =13824a(9) =140160a(10) =1263360a(11) =15298560a(12) =168422400a(13) =2373073920a(14) =30865121280a(15) =496199854080
External references
- oeis: A173841