Number of permutations of 1..n with no adjacent pair summing to n+5.
A173845
Number of permutations of 1..n with no adjacent pair summing to n+5.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =120a(6) =480a(7) =3600a(8) =23040a(9) =221760a(10) =1895040a(11) =22176000a(12) =235791360a(13) =3242695680a(14) =41153495040a(15) =649729382400
External references
- oeis: A173845