If anyone is interested in some fresh information on this subject contact me and let’s talk. My methods will allow you to design counters using T, D, & JK flip-flops. in any conceivable count sequence. You can also mix flip flop types and get the same results. I also have developed simple rule sets for creating binary to gray and gray to binary codes, and ways of generating Karnaugh maps beyond four bits, that are not confusing.