Number of permutations in S_{2n} avoiding 123 and 1432 whose matrices are 180-degree symmetric.
A166963
Number of permutations in S_{2n} avoiding 123 and 1432 whose matrices are 180-degree symmetric.
Terms
- a(0) =1a(1) =2a(2) =6a(3) =12a(4) =27a(5) =61a(6) =138a(7) =309a(8) =694a(9) =1560a(10) =3506a(11) =7877a(12) =17699a(13) =39770a(14) =89363a(15) =200796a(16) =451184a(17) =1013802a(18) =2277993a(19) =5118603a(20) =11501396a(21) =25843403a(22) =58069600a(23) =130481206a(24) =293188608a(25) =658788823a(26) =1480285049
External references
- oeis: A166963