[seqfan] Verification: 13 is or is not a square modulo 26

[Alonso Del Arte]

Just want to be sure to doublecheck this with at least one other person:
the nonsquares modulo 26 are 2, 5, 6, 7, 8, 11, 15, 18, 19, 20, 21, 24. So
13 is not on the list because if x = 13 mod 26, then x^2 = 13 mod 26 also.

Al