A393451 Consider the square spiral with its cells numbered starting at 0, as in A308884 and A274641. Two players, Black and Red, take turns. When it is Black's turn, he places a king at the smallest unoccupied cell not attacked by an existing Red king, and when it is Red's turn, she places a king at the smallest unoccupied cell not attacked by an existing Black king. Sequence lists squares occupied by a Red king.

9, 15, 16, 23, 24, 25, 26, 34, 35, 36, 37, 46, 47, 48, 49, 50, 51, 61, 62, 63, 64, 65, 66, 77, 78, 79, 80, 81, 82, 83, 84, 96, 97, 98, 99, 100, 101, 102, 103, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 190, 191, 192

Offset

0,1

Comments

Similar to A392177 and A392178, but placing kings instead of knights.

Links

Jonas Karlsson, Table of n, a(n) for n = 0..19999 (terms 0..9999 from Michael S. Branicky)

Michael S. Branicky, Python program for OEIS A393450 and A393451

Jonas Karlsson, Illustration of first 3200 squares of the sprial

Prog

(Python) # see linked program

Crossrefs

Cf. A393450 (Black kings). See also A308884, A274641, A392177, A392178 (knights).

For kings of a single color, see A307188.

Sequence in context: A105882 A136410 A324879 * A066942 A257048 A363896

Adjacent sequences: A393448 A393449 A393450 * A393452 A393453 A393454

Keyword

nonn

Author

Jonas Karlsson and N. J. A. Sloane, Apr 20 2026.

Status

approved