Find the number of ways of arranging the numbers 1, 2, 3, 9 in a circle, so that the sum of any three adjacent numbers is divisible by 3. (Two arrangements are considered the same if one arrangement can be rotated to obtain the other.)
Please do not post solutions to this problem!
This is a homework problem, and the original poster is trying to cheat. I know, because I am in the same class, and have the same homework.