Number of square permutations of n elements.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =12a(5) =60a(6) =270a(7) =1890a(8) =14280a(9) =128520a(10) =1096200a(11) =12058200a(12) =139043520a(13) =1807565760a(14) =22642139520a(15) =339632092800