A326421 -id:A326421 - cp's OEIS frontend

A326311 Least numbers k such that A004018(k) is nondecreasing.

0, 1, 2, 4, 5, 10, 13, 17, 20, 25, 50, 65, 85, 125, 130, 145, 170, 185, 205, 221, 250, 260, 265, 290, 305, 325, 425, 650, 725, 845, 850, 925, 1025, 1105, 1625, 1885, 2125, 2210, 2405, 2465, 2665, 3145, 3250, 3445, 3485, 3625, 3770, 3965, 4225, 5525

Offset: 1

Hugo Pfoertner, Sep 11 2019

nonn

Least squared radius of a circle around a grid point of the square 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 square lattice with smaller radius. a(1) = 0 by convention.

Hugo Pfoertner, Table of n, a(n) for n = 1..440

Cf. A004018, A071383, A071385, A326421.

using Nemo
function A326311List(len)
    R, x = PolynomialRing(ZZ, "x")
    e = theta_qexp(2, len, x)
    L = [coeff(e, j) for j in 0:len - 1]
    m = ZZ(0)
    [n - 1 for (n, l) in enumerate(L) if l == (m = max(m, l))]
end
A326311List(1000) |> println # Peter Luschny, Sep 12 2019

r2=0;for(k=0,6000,my(a004018 = if( k<1, k==0, 4 * sumdiv( k, d, (d%4==1) - (d%4==3))));if(a004018>=r2,r2=a004018;print1(k,", ")))

cp's OEIS Frontend

A326311 Least numbers k such that A004018(k) is nondecreasing.

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