%!PS

/cardano {
    /cn exch def
    /k 0 def
    {
        /a k 3 mul 2 add def
        /b2c k 1 add dup mul k 8 mul 5 add mul def
        /b 0 def
        /b2 0 def
        /inc 1 def
        {
            /b b 1 add def
            /b2 b2 inc add def
            /inc inc 2 add def
            b2 b2c gt {
                exit
            } if
            b2c b2 mod 0 eq {
                [ a b b2c b2 idiv ] ==
                /cn cn 1 sub def
                cn 0 le {
                    exit
                } if
            } if
        } loop
        cn 0 le {
            exit
        } if
        /k k 1 add def
    } loop
} bind def

5 cardano