It's all about the (Fibonacci) numbers.
This cache is in the form of a blue unusable bird house. It's located in the Knowlton Forest Trails area in Concord, NH about 125' west of the Red trail. Once you find the "bird house" you will have to do a few things to get to the log. You will need to know the Fibonacci Sequence up to at least 21. If necessary Google. A good site is https://www.mathsisfun.com/numbers/fibonacci-sequence.html
1. Unscrew the black knob on the bottom right of the house (facing the hole).
2. Swing the front up.
3. Inside is a red box with instructions which I will repeat here.
4. To open the combination lock, rotate the top dial to the largest single digit in the Fibonacci Sequence. (Lining up carefully with the red line).
5. Then turn the middle dial to the second largest single digit in the sequencde
6. Now turn the lowest dial to the third largest single digit in the sequence. (You will have 3 Fibonacci numbers in their descending order).
7. The lock should open. Open the box, Take the log out of container, sign, put log back in container, close container and then replace in box.
8, Replace the lock, close it and spin each dial. Please make sure the red lines are facing toward the front.
9. Lower the front and repalce the black knob.
10. Don't forget to log online....you're done.