for ($i = 1; $i < 2000; $i++) {
string $groupa = ("group"+$i+".visibility");
string $groupb = ("group"+$i+".v");
int $a = $i;
int $b = 3 + (($i - 1) * 2);
int $c = 5 + (($i - 1) * 2);
setAttr $groupa off;
setKeyframe -t $a $groupb;
setAttr $groupa on;
setKeyframe -t $b $groupb;
setAttr $groupa off;
setKeyframe -t $c $groupb;
}