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A216877 Number of ordered integers (x,y) satisfying x^(2/3) + y^(2/3) <= n^(2/3). 0
1, 5, 9, 17, 21, 33, 49, 61, 81, 105, 125, 145, 169, 205, 233, 273, 309, 357, 393, 437, 485, 529, 565, 629, 681, 741, 805, 873, 933, 997, 1073, 1133, 1205, 1289, 1377, 1453, 1537, 1633, 1725, 1793, 1889, 1989, 2081, 2177, 2293, 2393, 2497, 2621, 2721, 2833 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Lattice points in x^(2/3) + y^(2/3) <= n^(2/3).

LINKS

Table of n, a(n) for n=0..49.

MAPLE

count := proc(n)

    local t, x, y;

    t := 0;

    for x from 1 to n-1 do

      for y from 1 to n-x do

        if evalf(x^(2/3)+y^(2/3)-n^(2/3)) <= 0 then

          t := t+1

        end if:

      end do:

    end do;

    return 4*t+4*n+1:

  end proc;

  S := [seq(count(a), a = 0 .. 41)];

MATHEMATICA

Table[cnt = 0; Do[If[x^(2/3) + y^(2/3) <= n^(2/3), cnt++], {x, n}, {y, n}]; 4*cnt + 4*n + 1, {n, 0, 50}] (* T. D. Noe, Sep 18 2012 *)

CROSSREFS

Sequence in context: A288448 A022341 A255651 * A268756 A095725 A005006

Adjacent sequences:  A216874 A216875 A216876 * A216878 A216879 A216880

KEYWORD

nonn

AUTHOR

César Eliud Lozada, Sep 18 2012

STATUS

approved

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Last modified January 21 03:47 EST 2022. Contains 350473 sequences. (Running on oeis4.)