Okay i have 4 inputs, A,B,C,D, and when i put it into a K-map i got 5 terms, its a prime number circuit. It will output 1 if the number is prime, example... 2,3,5,7,11,13. So 1101 == 13 would output a 1. A = 1, B = 1, C = 0, D = 1; Output = 1 From suming up the min terms on my truth table i got the following boolean expression: Note: 'A means A complemented 'A'BC'D + 'A'BCD + 'AB'CD + 'ABCD + A'BCD + AB'CD I put it into a K-map and got the following: 'A'BC'D + 'ACD + 'ABD + 'BCD + B'CD Does that look right to you? I already wasted an hour implemented the wrong diagram because i screwed up the k-map and i want to make sure i didn't screw it up again. Thanks.