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

1,3

Comments

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.

Links

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

Prog

(PARI) 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, ", ")))
(Julia) 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

Crossrefs

Cf. A004018, A071383, A071385, A326421.

Sequence in context: A013578 A283204 A105138 * A325107 A064383 A018360

Adjacent sequences: A326308 A326309 A326310 * A326312 A326313 A326314

Keyword

nonn

Author

Hugo Pfoertner, Sep 11 2019

Status

approved