+321 We split it up into two cases, one where the first number is odd and one where the first number is even.
ODD: We have 3 choices for the first, 2 choices for the second, 3 choices for the third, and so on, giving us a number of 108 possible ways.
EVEN: We have 2 choices for the first, 3 choices for the second, 2 choices for the third, and so on, giving us a number of 72 possible ways.
108+72 = 180 possible combinations.
