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 A308890 Follow along the squares in the square spiral (as in A274640); in each square write the smallest positive number that a knight placed at that square cannot see. 5
 1, 1, 1, 1, 2, 2, 2, 3, 3, 2, 2, 2, 2, 3, 3, 2, 3, 4, 4, 3, 1, 2, 4, 3, 2, 1, 4, 4, 4, 3, 1, 2, 4, 4, 2, 1, 1, 1, 4, 4, 1, 1, 1, 3, 2, 4, 4, 1, 1, 1, 3, 3, 4, 3, 1, 1, 1, 3, 2, 4, 4, 2, 3, 1, 2, 1, 2, 2, 2, 2, 1, 2, 2, 3, 3, 2, 4, 3, 2, 1, 2, 2, 2, 3, 2, 2, 2, 2, 1, 2, 2, 3, 3, 2, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS Similar to A274640, except that here we consider the mex of squares that are a knight's moves rather than queen's moves. Since there are at most 4 earlier cells in the spiral at a knight's move from any square, a(n) <= 5. This is obtained by adding 1 to the terms of A308884. "Mex" here means minimal positive excluded value. LINKS Table of n, a(n) for n=1..95. CROSSREFS Cf. A247640, A274641, A308885-A308895. Sequence in context: A282495 A354226 A341421 * A081414 A328577 A094321 Adjacent sequences: A308887 A308888 A308889 * A308891 A308892 A308893 KEYWORD nonn AUTHOR N. J. A. Sloane, Jul 01 2019 STATUS approved

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Last modified April 24 04:14 EDT 2024. Contains 371918 sequences. (Running on oeis4.)