How many logarithms can be obtained by taking any two different numbers from 1, 2, 3, 4, 7 and 9 as the base and true number of logarithms respectively Same as above, please give me a process

How many logarithms can be obtained by taking any two different numbers from 1, 2, 3, 4, 7 and 9 as the base and true number of logarithms respectively Same as above, please give me a process

5 * 6 = 30 ㏒ with 2 as the bottom 4 = ㏒ with 3 as the bottom 9; ㏒ with 4 as the bottom 2 = ㏒ with 9 as the bottom 3; ㏒ with 2 as the bottom 3 = ㏒ with 4 as the bottom 9; ㏒ with 3 as the bottom 2 = ㏒ with 9 as the bottom 4; so remove 4; when 1 is the bottom number, it does not hold, so remove 5; when 1 is a true number, all 5 are 0, so remove 4; so 30-4-5-4 = 17