Number of permutations of 1..n with the Sum_{i=1..n} of (i-p(i))^2 <= (n-1)*n*(n+1)/6.
A180111
Number of permutations of 1..n with the Sum_{i=1..n} of (i-p(i))^2 <= (n-1)*n*(n+1)/6.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =3a(4) =13a(5) =63a(6) =360a(7) =2612a(8) =20628a(9) =184784a(10) =1814400a(11) =20168640a(12) =241650132a(13) =3135712971a(14) =43589145600a(15) =657203494738
External references
- oeis: A180111