A396975 - OEIS

%I #9 Jun 25 2026 08:33:05

%S 0,4,8,14,16,20,24,30,32,36,40,46,49,54,58,60,64,70,74,76,82,85,89,92,

%T 97,101,104,111,113,119,123,127,130,133,137,140,146,149,153,156,161,

%U 165,168,175,177,183,187,191,194,197,201,204,210,214,218,220,225,230

%N Follow along the squares in the Hilbert curve. Place a chess king at each square that is not attacked by an existing king. This sequence gives the squares occupied by the kings.

%H Rémy Sigrist, <a href="/A396975/b396975.txt">Table of n, a(n) for n = 1..10000</a>

%H Rémy Sigrist, <a href="/A396975/a396975.png">Representation of the first terms</a> (the color is function of x mod 2, y mod 2)

%H Rémy Sigrist, <a href="/A396975/a396975.gp.txt">PARI program</a>

%e The Hilbert curve begins:

%e      .---.  49---.---.   .---.---.

%e          |   |       |   |       |

%e     60---.   .---.  46---.  40---.

%e      |           |           |

%e      .   .---.   .   .---.   .---.

%e      |   |   |   |   |   |       |

%e     58---.  54---.  32   .--36---.

%e                      |

%e      .---.   .---.   .   .---.---.

%e      |   |   |   |   |   |       |

%e      4   .---8   .  30---.  24---.

%e      |           |           |

%e      .---.   .---.   .---.   .---.

%e          |   |       |   |       |

%e      0---.  14---.--16   .--20---.

%o (PARI) \\ See Links section.

%Y Cf. A059252, A059253, A307188, A397052.

%K nonn

%O 1,2

%A _Rémy Sigrist_, Jun 12 2026