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a(n) = least positive r <= n such that the origin-centered circle of radius sqrt(r) touches A071339(n) lattice points.
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%I #11 Jul 14 2024 03:49:10

%S 0,1,1,5,5,25,25,25,25,65,65,65,65,65,65,65,65,65,65,325,325,325,325,

%T 325,325,325,325,325,325,325,325,325,325,325,1105,1105,1105,1105,1105,

%U 1105,1105,1105,1105,1105,1105,1105,1105,1105,1105,1105,1105,1105,1105

%N a(n) = least positive r <= n such that the origin-centered circle of radius sqrt(r) touches A071339(n) lattice points.

%H Hugo Pfoertner, <a href="https://www.randomwalk.de/sequences/a071340.gif">Illustration</a>

%e a(4)=5 because the smallest circle to touch A071339(4)=8 points has radius sqrt(5).

%o (FORTRAN) See A071339.

%Y Cf. A071339-A071347.

%K easy,nonn

%O 0,4

%A _Hugo Pfoertner_, May 22 2002

%E Edited by _Don Reble_, Nov 06 2005