Write a shell script to generate following series1,3,2,4,3,5,4,6,----100

Write a shell script to generate following series
1,3,2,4,3,5,4,6,----100
num=1

while [ $num -le 98 ]
do
check=`expr $num % 2`
if [ $check -ne 0 ]
then
echo -n "$num"
odd=`expr $num + 2`
echo -n "$odd"
else
echo -n "$num"
even=`expr $num + 2`
echo -n "$even"
fi

num=`expr $num + 1`
done