Lua whileサイクル九九乗算表

a= 0

while(a<9)do
    local s=""
    b= 0
    a=a+1
    while(b<9)do
        b=b+1
        if (b<=a) then
        s=s..a.."x"..b.."="..a*b
            if a~=b then
            s=s.."\t"
           end
        end
    end
    print(s)
end
a=10
while(a>1)do 
    local s = ""
    a=a-1
    b=0
    while(b<9)do
        b=b+1
        if(b<=a)then
            s=s..string.format( "%dX%d=%d\t",a,b,a*b )
        end
    end
    print(s)
end