A326421 Least numbers k such that A088534(k) is nondecreasing.

0, 1, 3, 4, 7, 9, 12, 13, 16, 19, 21, 25, 27, 28, 31, 36, 37, 39, 43, 48, 49, 91, 133, 147, 169, 196, 217, 247, 259, 273, 301, 343, 361, 364, 399, 403, 427, 441, 469, 481, 507, 511, 532, 553, 559, 588, 589, 637, 931, 1183, 1519, 1729, 2821, 3367

Offset: 1

Author

Hugo Pfoertner, Sep 12 2019

Keywords

• nonn

Comments

Least squared radius of a circle around a grid point of the hexagonal lattice such that the number of grid points on this circle is not smaller than the number of grid points on any circle around a grid point of the hexagonal lattice with smaller radius. a(1) = 0 by convention.

Links

• Hugo Pfoertner, Table of n, a(n) for n = 1..163

Crossrefs

Cf. A003136, A088534, A118886, A230655, A326311.

Programs

PARI

\\ after M. F. Hasler's A088534(n,d)
r2=0;for(k=0,3500,my(a088534=sum(x=0, sqrt(k\3), sum(y=max(x, sqrtint(k-x^2)\2), sqrtint(k-2*x^2), x^2+x*y+y^2==k)));if(a088534>=r2,r2=a088534;print1(k,", ")))