Number of permutations of 1..n with no adjacent pair summing to n+4.
A173844
Number of permutations of 1..n with no adjacent pair summing to n+4.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =72a(6) =480a(7) =2640a(8) =23040a(9) =175680a(10) =1895040a(11) =18385920a(12) =235791360a(13) =2771112960a(14) =41153495040a(15) =567422392320
External references
- oeis: A173844