Number of permutations of 2 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 4.
A190825
Number of permutations of 2 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 4.
Terms
- a(0) =1a(1) =0a(2) =0a(3) =0a(4) =0a(5) =1a(6) =40a(7) =876a(8) =16924a(9) =332507a(10) =6944594a(11) =156127796a(12) =3783620060a(13) =98614428186
External references
- oeis: A190825