OFFSET
2,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 2..100
FORMULA
If n is even: a(n) = (2n)!.
If n is congruent to 1 mod 4: a(n) = (n!)^2 / 2.
If n is congruent to 3 mod 4: a(n) = (n!)^2.
PROG
(PARI) a(n) = if(n < 2, 0, if(n%2==0, (2*n)!, (n!)^2 / if(n%4==1, 2, 1))); \\ Andrew Howroyd, Jul 04 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Sharon Sela (sharonsela(AT)hotmail.com), May 14 2002
EXTENSIONS
Terms a(8) and beyond from Andrew Howroyd, Jul 04 2018
STATUS
approved