Ahh you’re of course correct, might still be useful if you don’t memorise the mapping. I should have gone with my gut and generated the first 100 with each sch

Ahh you’re of course correct, might still be useful if you don’t memorise the mapping. I should have gone with my gut and generated the first 100 with each scheme to look at what the distribution looks like. Mod 19 scheme feels like it should be decent but it gives 10 half the probability of any other number. I did find a quick fix that may still be simple enough: take the number mod 19, and add the last digit of the original number. Now take the last digit of the sum, and add 1. So new guess = 1 + (n mod 19 + n mod 10) mod 10. Doing a quick simulation there is no obvious bias.