OFFSET
4,1
LINKS
J. B. Kadane, Some equivalence classes in paired comparisons, The Annals of Mathematical Statistics, 37 (1966), 488-494.
FORMULA
a(n) = n!*(n - 3 + (1/18)*(n - 4)*(n - 5)) (proven by Kadane).
EXAMPLE
For n = 4 the a(4) = 24 solution is 4!*(4 - 3 + (1/18)*(4 - 4)*(4 - 5)) = 24.
PROG
(R) fact(n)*(n-3+(1/18)*(n-4)*(n-5))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ian R Harris, Sep 19 2022
STATUS
approved