Number of permutations of 2 copies of 1..n with all adjacent differences <= 2 in absolute value.
A177283
Number of permutations of 2 copies of 1..n with all adjacent differences <= 2 in absolute value.
Terms
- a(0) =1a(1) =1a(2) =6a(3) =90a(4) =660a(5) =3846a(6) =24326a(7) =148146a(8) =850920a(9) =4788114a(10) =26548704a(11) =144707622a(12) =778116870a(13) =4140736398a(14) =21836757474a(15) =114262071558a(16) =593931441790
External references
- oeis: A177283