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The program I wrote to find Lattice Circles for

Enigma 136can also be used to solve this problem. It runs in 185ms.Solution:The radius of the smallest circle with exactly 5 lattice points is (25/6)√2 (≈ 5.893). The circle is centred on (1/6, 1/6).The original solution published was that the minimum possible radius is 6.25 (25/4), centred on (1/4, 0), which does indeed give a circle with 5 lattice points, but it is not the smallest possible.

A correction was published with

Enigma 237.