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 A060465 Value of x of the solution to x^3 + y^3 + z^3 = A060464(n) (numbers not 4 or 5 mod 9) with smallest |z| and smallest |y|, 0 <= |x| <= |y| <= |z|. 4

%I

%S 0,0,0,1,-1,0,0,0,1,-2,7,-1,-511,1,-1,0,1,-11,-2901096694,-1,0,0,0,1,

%T -283059965,-2736111468807040,-1,0,1,0,1,117367

%N Value of x of the solution to x^3 + y^3 + z^3 = A060464(n) (numbers not 4 or 5 mod 9) with smallest |z| and smallest |y|, 0 <= |x| <= |y| <= |z|.

%C Indexed by A060464.

%C Only primitive solutions where gcd(x,y,z) does not divide n are considered.

%C From the solution A060464(24) = 30 = -283059965^3 - 2218888517^3 + 2220422932^3 (smallest possible magnitudes according to A. Bogomolny), one has a(24) = -283059965. A solution to A060464(25) = 33 remains to be found. Other values for larger n can be found in the first column of the table on Hisanori Mishima's web page. - _M. F. Hasler_, Nov 10 2015

%D R. K. Guy, Unsolved Problems in Number Theory, 3rd ed., Springer, New York, 2004, Section D5, 231-234.

%H D. J. Bernstein, <a href="http://cr.yp.to/threecubes.html">Three cubes</a>

%H A. Bogomolny, <a href="http://www.cut-the-knot.org/arithmetic/algebra/FinikyDiophantineEquations.shtml">Finicky Diophantine Equations</a> on cut-the-knot.org, accessed Nov. 10, 2015

%H B. Conn, L. Vaserstein, <a href="http://www.ams.org/bookstore?fn=20&amp;arg1=conmseries&amp;ikey=CONM-166">On sums of three integral cubes</a>, Contemp. Math 166 (1994) <a href="http://www.ams.org/mathscinet-getitem?mr=1284068">MR1284068</a>

%H V. L. Gardiner, R. B. Lazarus, P. R. Stein, <a href="http://dx.doi.org/10.1090/S0025-5718-1964-0175843-9">Solutions of the diophantine equation x^3+y^3=z^3-d</a>, Math. Comp. 18 (1964) 408-413.

%H D.R. Heath-Brown, W.M. Lioen and H.J.J. te Riele <a href="http://euler.free.fr/docs/HLR93.pdf"> on Solving the Diophantine Equation x3 + y3 + z3 = k on a Vector Computer</a>

%H J. C. P. Miller, M. F. C. Woollett, <a href="http://dx.doi.org/10.1112/jlms/s1-30.1.101">Solutions of the Diophantine Equation x^3+y^3+z^3=k</a>, J. Lond. Math. Soc. 30 (1) (1955) 101-110

%H Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/math04/matb0100.htm">About n=x^3+y^3+z^3</a>

%e For n=16 the smallest solution is 16 = (-511)^3 + (-1609)^3 + 1626^3, which gives the term -511.

%t (* this program is not convenient for hard cases *) nmax = 29; xmin[_] = 0; xmax[_] = 20; xmin[16] = 500; xmax[16] = 600; xmin[24] = 2901096600; xmax[24] = 2901096700; r[n_, x_] := Reduce[0 <= Abs[x] <= Abs[y] <= Abs[z] && n == x^3 + y^3 + z^3, {y, z}, Integers]; r[n_ /; IntegerQ[n^(1/3)]] := {0, 0, n^(1/3)}; mySort = Sort[#1, Which[Abs[#1[[3]]] <= Abs[#2[[3]]], True, Abs[#1[[3]]] == Abs[#2[[3]]], If[Abs[#1[[2]]] <= Abs[#2[[2]]], True, False], True, False] & ] & ; rep := {x_, y_, z_} /; (x + y == 0 && x > 0) :> {-x, -y, z}; r[n_] := Reap[Do[ sp = r[n, x] /. C[1] -> 1; If[sp =!= False, xyz = {x, y, z} /. {ToRules[sp]} /. rep; If[GCD @@ Flatten[{n, xyz}] == 1, Sow[xyz]]]; sn = r[n, -x] /. C[1] -> 1; If[sn =!= False, xyz = {-x, y, z} /. {ToRules[sn]} /. rep; If[GCD @@ Flatten[{n, xyz}] == 1, Sow[xyz]]], {x, xmin[n], xmax[n]}]][[2, 1]] // Flatten[#, 1] & // mySort // First; A060464 = Select[Range[0, nmax], Mod[#, 9] != 4 && Mod[#, 9] != 5 &]; A060465 = Table[xyz = r[n]; Print[ " n = ", n, " {x,y,z} = ", xyz]; xyz[[1]], {n, A060464}] (* _Jean-François Alcover_, Jul 10 2012 *)

%Y Cf. A060466, A060467, A173515.

%K sign,nice,hard,more

%O 0,10

%A _N. J. A. Sloane_, Apr 10 2001

%E Edited and a(24) added by _M. F. Hasler_, Nov 10 2015

%E a(25) from Tim Browning and further terms added by _Charlie Neder_, Mar 09 2019

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Last modified December 7 03:00 EST 2019. Contains 329836 sequences. (Running on oeis4.)