OFFSET
0,4
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
FORMULA
a(n) = n! - n!!.
EXAMPLE
a(7) = 7*6*5*4*3*2*1 - 7*5*3*1 = 4935.
MATHEMATICA
Table[(n!-n!!), {n, 0, 15}] (* Zerinvary Lajos, Mar 21 2007 *)
PROG
(PARI) a(n)={n! - if(n%2, n!/((n\2)!*2^(n\2)), (n/2)!*2^(n/2))} \\ Andrew Howroyd, Jan 02 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paolo P. Lava, Sep 21 2005
EXTENSIONS
Terms a(15) and beyond from Andrew Howroyd, Jan 02 2020
STATUS
approved