Number of permutations p of {1,2,3...,n} that are fixed points under the operation of first reversing p, then taking the inverse.
A037224
Number of permutations p of {1,2,3...,n} that are fixed points under the operation of first reversing p, then taking the inverse.
Terms
- a(0) =1a(1) =0a(2) =0a(3) =2a(4) =2a(5) =0a(6) =0a(7) =12a(8) =12a(9) =0a(10) =0a(11) =120a(12) =120a(13) =0a(14) =0a(15) =1680a(16) =1680a(17) =0a(18) =0a(19) =30240a(20) =30240a(21) =0a(22) =0a(23) =665280a(24) =665280a(25) =0a(26) =0a(27) =17297280a(28) =17297280a(29) =0
External references
- oeis: A037224