login
A212397
Denominator of the average number of move operations required by an insertion sort of n (distinct) elements.
3
1, 1, 2, 6, 6, 30, 5, 35, 140, 1260, 1260, 13860, 13860, 180180, 180180, 180180, 360360, 6126120, 2042040, 38798760, 7759752, 2586584, 2586584, 59491432, 178474296, 4461857400, 4461857400, 40156716600, 40156716600, 1164544781400, 1164544781400
OFFSET
0,3
COMMENTS
The average number of move operations is 1/n! times the number of move operations required to sort all permutations of [n] (A212395), assuming that each permutation is equiprobable.
FORMULA
a(n) = denominator of A212395(n)/A000142(n).
MAPLE
b:= proc(n) option remember;
`if`(n=0, 0, b(n-1)*n + (n-1)! * (n-1)*(n+4)/2)
end:
a:= n-> denom(b(n)/n!):
seq(a(n), n=0..30);
MATHEMATICA
a[n_] := Denominator[n (n + 7)/4 - 2 HarmonicNumber[n]];
Table[a[n], {n, 0, 30}] (* _Jean-François Alcover_, May 29 2018, from 2nd formula in A212396 *)
CROSSREFS
Numerators are in A212396.
Sequence in context: A085087 A072983 A055204 * A008339 A077139 A068629
KEYWORD
nonn,frac
AUTHOR
_Alois P. Heinz_, May 14 2012
STATUS
approved