shell script to create a set of each 3 values within a range

I am trying to create a set of each 3 values within a range using Shell script.

Range of values     : 512 -885
Column difference: 12
Column increment: 3

    512 524 536
    515 527 539
    518 530 542
                 ......
    860 872 884
    863 875 513  --> Column 3 Reset
    866 878 516
    869 881 519
    872 884 522
    875 513 525  --> Column 2 Reset
    878 515 528
    881 518 531
    884 521 534
    513 524 537
    ....

Shell Script:

#!/bin/bash

start=512

end=885

incr=12

col1=$start

col2=$(($col1+$incr))

col3=$(($col2+$incr))

colincr=3

for z in {1..50}

do

    if [ $col1 -gt $end ]

    then

        col1=$(($(($col1 % $end))+$start-1))

    fi

    if [ $col2 -gt $end ]

    then

        col2=$(($(($col2 % $end))+$start-1))

    fi

    if [ $col3 -gt $end ]

    then

        col3=$(($(($col3 % $end))+$start-1))

    fi

    printf '%-4s%-4s%-4s\n' $col1 $col2 $col3

    col1=`expr $col1 + $colincr`

    col2=`expr $col2 + $colincr`

    col3=`expr $col3 + $colincr`

    

done