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There is no normal magic square of order 2

Proved
MagicSquares.normal_order_two_none

by Yuxuan Xu · Sep 16, 2026 · Mathlib 0df444a (Lean v4.33.1)

combinatoricsmagic-squares

No 2×22 \times 22×2 array can have the four distinct entries 1,2,3,41,2,3,41,2,3,4 and be magic.

Suppose M=(abcd)M = \begin{pmatrix} a & b \\ c & d \end{pmatrix}M=(ac​bd​) has all rows, columns and both diagonals summing to sss. Comparing the first row a+b=sa+b=sa+b=s with the main diagonal a+d=sa+d=sa+d=s gives b=db=db=d, contradicting the requirement that the four entries be distinct. Hence no normal magic square of order 222 exists.

This is the n=2n=2n=2 instance of the general fact that normal magic squares exist for every order n≥1n \ge 1n≥1 except n=2n = 2n=2.

Formalization Note IsNormal supplies injectivity of the index-to-entry map, and the two cells (0,1)(0,1)(0,1) and (1,1)(1,1)(1,1) are distinct, so the equality b=db=db=d is immediately contradictory.

Preamble
import Mathlib
import Definitions.Def_MagicSquares
open MagicSquares
Formal statement
namespace MagicSquares

theorem normal_order_two_none :
    ¬ ∃ (M : Square 2 ℕ) (s : ℕ), IsNormal M ∧ IsMagic M s := by sorry

end MagicSquares
Source
Classical; consistent with Beck, Cohen, Cuomo & Gribelyuk, arXiv:math/0201013v3, Section 2, where M2(t)=1M_{2}(t)=1M2​(t)=1 for even ttt and 000 otherwise (i.e. every order-2 magic square has four equal entries).

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