Yes, my cipher is exactly the same as four rounds of Vigenère with 2,3,5,7 length keys, with the proviso that you can't go beyond 210 when all four keys meet ag

Yes, my cipher is exactly the same as four rounds of Vigenère with 2,3,5,7 length keys, with the proviso that you can't go beyond 210 when all four keys meet again. (I may go back and edit the text to make this clear.)