Number of stretching pairs in all permutations in S_n.
A216119
Number of stretching pairs in all permutations in S_n.
Terms
- a(0) =0a(1) =0a(2) =0a(3) =2a(4) =30a(5) =360a(6) =4200a(7) =50400a(8) =635040a(9) =8467200a(10) =119750400a(11) =1796256000a(12) =28540512000a(13) =479480601600
External references
- oeis: A216119