If I had kept with my thinking that the 1st 2 digits would come from Odd #'s pairs there would have been 10 possible pair combinations to consider. 00 01 04 05 08 09 45 48 49 58 59 89
When I say Odd #ed pairs, what I do is pair 2 digits together and then number the groups. 01 is Group 1; 23 is Group 2; 45 is group 3; 67 is group 4; and 89 is group 5. The Odd numbered pairs would be Groups 1-3 and 5. The 2-3-6-7 would have been eliminated.
That would have been 10 possible pairs. Then if I trac how many "pairs" the two digits come from it would have been further reduced to 04 05 08 09 14 15 18 19 48 49 59 58. This would have been 12 pairs to consider.
Then if you look at the Sum Total of the pair and could determine was less then 11 you could eliminate 4 of the 12 pair leaving 8. Then consider will the Sum be Odd or Even? Going Odd that would sliminate 4 more pair leaving only the 05 09 14 and 18.
It's simply a process of Elimination for Determination. Total pairs derived from just 6 digits gives you 22 pairs. This is less then half the 55 pairs there are of 10 digits 0 through 9.
I track the pairs by their assigned number and not the pairs themselves. When I can eliminate all pairs that are Odd numbered I have only digits 2-3-6-7 to work with. 23 26 27 36 37 67 . Makes it nice to be able to cut those pairs down.
If you determine something for a specific position like saying these two digits are going to be the front pairs and these two the back pair, there is no need to Box the combinations and play all the exact positionis involved the 4 digits you use.
Couldn't do that for the 2nd pair today though.