*Note:*

*Cn is column number, reading left to right.*

*Rn is row number, reading top to bottom.*

The starting board:

The most obvious feature of this board is the matching Head and Tail. Notice there is only one pair of 5s. If you can eliminate them, you will have made your task exponentially easier. Notice that the sequence between the 5s is not symmetric.

One way to introduce symmetry is to Check, then try to eliminate the numbers between the last of a pair and the new first of the pair. As always, Check and survey.

Notice in the first column you can eliminate the fives vertically. Then notice the symmetry revealed.

First eliminate the 1s via vertical elimination: C1R4 – C1R5. Then eliminate the 5s: C1R3 – C1R6.

This creates a series of horizontal eliminations (a symmetric sequence) starting with a pair of 1s: C9R2 – C2R3. This creates a horizontal elimination of 4 – 6, then 1 – 1, then 3 – 7, then 1 – 1, then 2 – 8, then 1 – 1, then 1 – 9.

Now, eliminate R1 vertically with R4 (and the obvious C1R1 – C1R2 vertical match).

Now, notice the symmetric sequence. Eliminate C2R6 – C9R5, leaving a 4 – 6 match, then 1 – 1, then 3 – 7, then 1 – 1, then 2 – 8, then 1 – 1, then 1 – 9.