A180112 Number of permutations of 1..n with the Sum_{i=1..n} of (i-p(i))^2 < (n-1)*n*(n+1)/6.

1, 3, 11, 57, 360, 2428, 19692, 178096, 1814400, 19748160, 237351468, 3091307829, 43589145600, 650470873262, 10415387654044, 177171175431551, 3201186852864000, 60647963017860105, 1213361365706836584, 25488014447816087399, 562000363888803840000

Offset

2,2

Links

Table of n, a(n) for n=2..22.

Formula

a(n) = A000142(n)/2 - A056876(n)/2. - Alois P. Heinz, May 07 2013

Crossrefs

Sequence in context: A052442 A217034 A330351 * A188458 A212435 A001586

Adjacent sequences: A180109 A180110 A180111 * A180113 A180114 A180115

Keyword

nonn

Author

R. H. Hardin, Aug 10 2010

Extensions

a(16)-a(19) from Robert Gerbicz, Nov 27 2010

a(20)-a(22) from Alois P. Heinz, May 07 2013

Status

approved