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A180111 Number of permutations of 1..n with the Sum_{i=1..n} of (i-p(i))^2 <= (n-1)*n*(n+1)/6. 0
1, 1, 3, 13, 63, 360, 2612, 20628, 184784, 1814400, 20168640, 241650132, 3135712971, 43589145600, 657203494738, 10507402233956, 178516252664449, 3201186852864000, 60997137390971895, 1219540642469803416, 25602927723893352601, 562000363888803840000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..22.

FORMULA

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

CROSSREFS

Sequence in context: A284716 A107097 A202837 * A292183 A006923 A283667

Adjacent sequences:  A180108 A180109 A180110 * A180112 A180113 A180114

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 10 2010

EXTENSIONS

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

a(1), a(20)-a(22) from Alois P. Heinz, May 07 2013

STATUS

approved

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Last modified April 24 18:03 EDT 2019. Contains 322430 sequences. (Running on oeis4.)