OFFSET
0,2
EXAMPLE
a(3)=5 because using {x, x+1, x+2, x+3} we can get x+1-x=1, x+2-x=2, x+3-x=3, (x+2-x)*(x+3-(x+1))=4 but we cannot obtain 5 in the same way.
CROSSREFS
KEYWORD
hard,more,nice,nonn
AUTHOR
Koksal Karakus (karakusk(AT)hotmail.com), Jun 13 2002
STATUS
approved