Barker sequences and circulant Hadamard matrices

About this app

Radar pulses of + and − whose echo peaks only at exact alignment: flip squares, see the echo live and as a sliding animation, complete search over all lengths up to 48 (hits only at 2, 3, 4, 5, 7, 11, 13), circulant matrix with order 4 and a check of order 16. Result from openai/math (family 179, formalised in Lean): circulant Hadamard matrices exist only in orders 1 and 4.

Subject: Open problems, solved by AI

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