A106265 -id:A106265 - cp's OEIS frontend

A106266 Least b such that A106265(n) + b^2 = c^3 for some c (given in A106267).

0, 5, 2, 1, 0, 4, 70, 7, 3, 18, 14, 2, 10, 1, 0, 6, 36, 5, 52, 9, 96, 13, 4, 524, 26, 17, 3, 76, 2, 8, 1, 0, 110, 21, 12, 985, 7, 89, 46, 140, 16, 6, 11, 5, 25, 35, 1710, 4, 20, 3, 15, 2, 1, 0, 57, 63, 40, 9, 322, 51, 2723, 14, 2765, 2315, 19, 8, 24, 364, 29

Offset: 1

Zak Seidov, Apr 28 2005

nonn

The values A106266(n) = 0 correspond to cubes A106265(n) = c^3. See the main entry A106265 for further comments and references.

M. F. Hasler, Table of n, a(n) for n = 1..2500 (corrected and extended Aug 10 2024)

Cf. A106265 (main entry), A106266 (the b-values).

[sqrtint(is_A106265(a)^3-a) | a<-A106265] \\ Assumes is_A106265(a) returns the c-value corresponding to a, and A106265 is a list or vector of values of that sequence. -M. F. Hasler, Aug 10 2024

a(n) = sqrt(A106267(n)^3-A106265(n)). - M. F. Hasler, Oct 05 2013

More terms from Robert G. Wilson v, Apr 28 2005

Edited by M. F. Hasler, Oct 04 2013

A106267 Least c such that A106265(n) + b^2 = c^3 for some b (given in A106266).

Original entry on oeis.org

1, 3, 2, 2, 2, 3, 17, 4, 3, 7, 6, 3, 5, 3, 3, 4, 11, 4, 14, 5, 21, 6, 4, 65, 9, 7, 4, 18, 4, 5, 4, 4, 23, 8, 6, 99, 5, 20, 13, 27, 7, 5, 6, 5, 9, 11, 143, 5, 8, 5, 7, 5, 5, 5, 15, 16, 12, 6, 47, 14, 195, 7, 197, 175, 8, 6, 9, 51, 10, 6, 59, 13, 7, 11, 6

Offset: 1

Zak Seidov, Apr 28 2005

nonn

M. F. Hasler, Table of n, a(n) for n = 1..2500 (replacing an incomplete version from 2013), Aug 10 2024

Cf. A106265 (main entry), A106266 (the b-values).

for(a=1, 999, (c=is_A106265(a))&& print1(c", ")) \\ M. F. Hasler, Oct 04 2013, edited Aug 10 2024: main program moved to A106265, as function is_A106265 which returns the (least) c-value a(n), always nonzero for terms of A106265, or 0 if the argument isn't a term of A106265.

a(n) = (A106265(n) + A106266(n)^2)^(1/3). - M. F. Hasler, Oct 04 2013

More terms from Robert G. Wilson v, Apr 28 2005
All values recomputed from A106266 and A106265 by R. J. Mathar, Aug 24 2008
Initial term 1 and other solutions with b=0 added by M. F. Hasler, Oct 04 2013

A081121 Numbers k such that Mordell's equation y^2 = x^3 - k has no integral solutions.

Original entry on oeis.org

3, 5, 6, 9, 10, 12, 14, 16, 17, 21, 22, 24, 29, 30, 31, 32, 33, 34, 36, 37, 38, 41, 42, 43, 46, 50, 51, 52, 57, 58, 59, 62, 65, 66, 68, 69, 70, 73, 75, 77, 78, 80, 82, 84, 85, 86, 88, 90, 91, 92, 93, 94, 96, 97, 98, 99

Offset: 1

T. D. Noe, Mar 06 2003

Mordell's equation has a finite number of integral solutions for all nonzero k. Gebel computes the solutions for k < 10^5. Sequence A054504 gives k for which there are no integral solutions to y^2 = x^3 + k. See A081120 for the number of integral solutions to y^2 = x^3 - n.
This is the complement of A106265. - M. F. Hasler, Oct 05 2013
Numbers k such that A081120(k) = 0. - Charles R Greathouse IV, Apr 29 2015

T. M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, page 191.

T. D. Noe, Table of n, a(n) for n = 1..7757 (from Gebel, 3136 and 6789 removed by _Seth A. Troisi_, May 20 2019)
J. Gebel, Integer points on Mordell curves [Cached copy, after the original web site tnt.math.se.tmu.ac.jp was shut down in 2017]
J. Gebel, A. Petho and G. Zimmer, On Mordell's equation, Compositio Mathematica 110 (3) (1998), 335-367. MR1602064.
Eric Weisstein's World of Mathematics, Mordell Curve

Cf. A054504, A081120, A106265.

m = 99; f[_List] := (xm = 2 xm; ym = Ceiling[xm^(3/2)];
Complement[Range[m], Outer[Plus, -Range[0, ym]^2, Range[-xm, xm]^3] //Flatten //Union]); xm=10; FixedPoint[f, {}] (* Jean-François Alcover, Apr 29 2011 *)

A179388 Values y for records of minima of positive distances d = A179386(n) = A154333(x) = x^3 - y^2.

Original entry on oeis.org

5, 11, 181, 207, 225, 500, 524, 1586, 13537, 376601, 223063347, 911054064, 16073515093, 22143115844, 29448160810, 1661699554612, 2498973838515, 26588790747913, 27582731314539, 178638660622364

Offset: 1

Artur Jasinski, Jul 12 2010, Jul 13 2010, Aug 03 2010

"Records of minima" means values A179386(n)=A154333(x) such that A154333(x') > A154333(x) for all x' > x, or equivalently A181138(y) such that A181138(y') > A181138(y) for all y' > y. See the main entry A179386 for all further considerations. - M. F. Hasler, Sep 30 2013
For d values see A179386, for x values see A179387.
Theorem (Artur Jasinski):
For any positive number x >= A179387(n), the distance between the cube of x and the square of any y (with x<>n^2 and y<>n^3) can't be less than A179386(n).
Proof: Because number of integral points of each Mordell elliptic curve of the form x^3-y^2 = k is finite and completely computable there can't exist any such x (or the related y).

Cf. A179107, A179108, A179109, A179387, A179388.

Cf. A181138, A229618, A077116, A106265, A165288.

max = 1000; vecd = Table[10100, {n, 1, max}]; vecx = Table[10100, {n, 1, max}]; vecy = Table[10100, {n, 1, max}]; len = 1; min = 10100; Do[m = Floor[(n^3)^(1/2)]; k = n^3 - m^2; If[k != 0, If[k <= min, ile = 0; Do[If[vecd[[z]] < k, ile = ile + 1], {z, 1, len}]; len = ile + 1; min = 10100; vecd[[len]] = k; vecx[[len]] = n; vecy[[len]] = m]], {n, 1, 13333677}]; dd = {}; xx = {}; yy = {}; Do[AppendTo[dd, vecd[[n]]]; AppendTo[xx, vecx[[n]]]; AppendTo[yy, vecy[[n]]], {n, 1, len}]; yy (*Artur Jasinski*)

A179388(n) = sqrt(A179387(n)^3 - A179386(n)).

Edited by M. F. Hasler, Sep 30 2013

A050801 Numbers k such that k^2 is expressible as the sum of two positive cubes in at least one way.

Original entry on oeis.org

3, 4, 24, 32, 81, 98, 108, 168, 192, 228, 256, 312, 375, 500, 525, 588, 648, 671, 784, 847, 864, 1014, 1029, 1183, 1225, 1261, 1323, 1344, 1372, 1536, 1824, 2048, 2187, 2496, 2646, 2888, 2916, 3000, 3993, 4000, 4200, 4225, 4536, 4563, 4644, 4704, 5184, 5324

Offset: 1

Patrick De Geest, Sep 15 1999

Analogous solutions exist for the sum of two identical cubes z^2 = 2*r^3 (e.g., 864^2 = 2*72^3). Values of 'z' are the terms in A033430, values of 'r' are the terms in A001105.
First term whose square can be expressed in two ways is 77976; 77976^2 = 228^3 + 1824^3 = 1026^3 + 1710^3. - Jud McCranie
First term whose square can be expressed in three ways is 3343221000; 3343221000^2 = 279300^3 + 2234400^3 = 790020^3 + 2202480^3 = 1256850^3 + 2094750^3.
First term whose square can be expressed in four ways <= 42794271007595289; 42794271007595289^2 = 14385864402^3 + 122279847417^3 = 55172161278^3 + 118485773289^3 = 64117642953^3 + 116169722214^3 = 96704977369^3 + 97504192058^3.
First term whose square can be expressed in five ways <= 47155572445935012696000; 47155572445935012696000^2 = 94405759361550^3 + 1305070263601650^3 = 374224408544280^3 + 1294899176535720^3 = 727959282778000^3 + 1224915311765600^3 = 857010857812200^3 + 1168192425418200^3 = 1009237516560000^3 + 1061381454915600^3.
After a(1) = 3 this is always composite, because factorization of the polynomial a^3 + b^3 into irreducible components over Z is a^3 + b^3 = (b+a)*(b^2 - ab + b^2). They may be semiprimes, as with 671 = 11 * 61, and 1261 = 13 * 97. The numbers can be powers in various ways, as with 32 = 2^5, 81 = 3^4, 256 = 2^8, 784 = 2^4 * 7^2 , 1225 = 5^2 * 7^2, and 2187 = 3^7. - Jonathan Vos Post, Feb 05 2011
If n is a term then n*b^3 is also a term for any b, e.g., 3 is a term hence 3*2^3 = 24, 3*3^3 = 81 and also 3*4^3 = 192 are terms. Sequence of primitive terms may be of interest. - Zak Seidov, Dec 11 2013
First noncubefree primitive term is 168 = 21*2^3 (21 is not a term of the sequence). - Zak Seidov, Dec 16 2013
From XU Pingya, Apr 10 2021: (Start)
Every triple (a, b, c) (with a^2 = b^3 + c^3) can produce a nontrivial parametric solution (x, y, z) of the Diophantine equation x^2 + y^3 + z^3 = d^4.
For example, to (1183, 65, 104), there is such a solution (d^2 - (26968032*d)*t^3 + 1183*8232^3*t^6, (376*d)*t - 65*8232^2*t^4, (92*d)*t - 104*8232^2*t^4).
To (77976, 228, 1824), there is (d^2 - (272916*d)*t^3 + 77976*57^3*t^6, (52*d)*t - 228*57^2*t^4, (74*d)*t - 1824*57^2*t^4).
Or to (77976, 1026, 1719), there is (d^2 - (25992*d)*t^3 + 77976*19^3*t^6, (37*d)*t - 1026*19^2*t^4, (11*d)*t - 1710*19^2*t^4). (End)

			1183^2 = 65^3 + 104^3.

Ian Stewart, "Game, Set and Math", Chapter 8, 'Close Encounters of the Fermat Kind', Penguin Books, Ed. 1991, pp. 107-124.

Chai Wah Wu, Table of n, a(n) for n = 1..10000 (terms 1..612 from T. D. Noe, terms 613..1000 from Harry J. Smith)

Cf. A050802, A000404, A033430, A001105, A038597, A050803, A106265, A217248.

A050801 := proc(n)
    option remember ;
    local a,x,y ;
    if n =1 then
        3
    else
        for a from procname(n-1)+1 do
            for x from 1 do
                if x^3 >= a^2 then
                    break ;
                end if;
                for y from 1 to x do
                    if x^3+y^3 = a^2 then
                        return a ;
                    end if;
                end do:
            end do:
        end do:
    end if;
end proc:
seq(A050801(n),n=1..20) ; # R. J. Mathar, Jan 22 2025

Select[Range[5350], Reduce[0 < x <= y && #^2 == x^3 + y^3, {x,y}, Integers] =!= False &] (* Jean-François Alcover, Mar 30 2011 *)
Sqrt[#]&/@Union[Select[Total/@(Tuples[Range[500],2]^3),IntegerQ[ Sqrt[ #]]&]] (* Harvey P. Dale, Mar 06 2012 *)
Select[Range@ 5400, Length@ DeleteCases[PowersRepresentations[#^2, 2, 3], w_ /; Times @@ w == 0] > 0 &] (* Michael De Vlieger, May 20 2017 *)

is(n)=my(N=n^2); for(k=sqrtnint(N\2,3),sqrtnint(N-1,3), if(ispower(N-k^3,3), return(n>1))); 0 \\ Charles R Greathouse IV, Dec 13 2013

a(n) = sqrt(A050802(n)). - Jonathan Sondow, Oct 28 2013

More terms from Michel ten Voorde and Jud McCranie

A050802 Squares expressible as the sum of two positive cubes in at least one way.

Original entry on oeis.org

9, 16, 576, 1024, 6561, 9604, 11664, 28224, 36864, 51984, 65536, 97344, 140625, 250000, 275625, 345744, 419904, 450241, 614656, 717409, 746496, 1028196, 1058841, 1399489, 1500625, 1590121, 1750329, 1806336, 1882384, 2359296

Offset: 1

Patrick De Geest, Sep 15 1999

			E.g., 717409 = 847^2 = 33^3 + 88^3.
169 = 13^2 = (-7)^3 + 8^3 is not a member, because 169 is not the sum of two positive cubes. - _Jonathan Sondow_, Oct 28 2013

"Game, Set and Math" by Ian Stewart, Chapter 8 'Close Encounters of the Fermat Kind', Penguin Books, Ed. 1991, pp. 107-124.

Tony D. Noe and Harry J. Smith, Table of n, a(n) for n = 1..1000
Index entries for sequences related to sums of squares

Cf. A038597, A050801, A050803, A106265, A217248.

ok[n_] := Length[Select[PowersRepresentations[n, 2, 3], #[[1]] != 0 & ]] >= 1; Select[Range[1600]^2, ok]
(* Jean-François Alcover, Apr 22 2011 *)
Union[Select[Total/@Tuples[Range[250]^3,2],IntegerQ[Sqrt[#]]&]] (* Harvey P. Dale, Mar 04 2012 *)

{ nstart=1; a2start=9; n=nstart; a=sqrtint(a2start)-1; until (0, a=a+1; a2=a*a; b1=((a2/2)^(1/3))\1; for (b=b1, a, b3=b*b*b; c1=1; if (a2 > b3, c1=((a2-b3)^(1/3))\1;); for (c=c1, b, d=b3 + c*c*c; if (d > a2 && c == 1, break(2)); if (d > a2, break); if (a2 == d, print(n, " ", a2); write("b050802.txt", n, " ", a2); n=n+1; break(2); ); ) ) ) } \\ Harry J. Smith, Jan 15 2009

is(n)=for(k=sqrtnint((n+1)\2,3),sqrtnint(n-1,3),if(ispower(n-k^3,3),return(issquare(n))));0 \\ Charles R Greathouse IV, Oct 28 2013

a(n) = A050801(n)^2. - Jonathan Sondow, Oct 28 2013

More terms from Michel ten Voorde

Definition corrected by Jonathan Sondow, Oct 28 2013

A165288 Possible values of the difference between a cube and the largest square not larger than the cube.

Original entry on oeis.org

0, 2, 4, 7, 11, 13, 19, 20, 26, 28, 35, 39, 40, 45, 47, 48, 49, 53, 55, 56, 60, 63, 67, 74, 76, 79, 81, 83, 100, 104, 107, 109, 116, 135, 139, 146, 147, 148, 150, 152, 155, 170, 174, 180, 184, 186, 191, 193, 200, 207, 212, 215, 216, 233, 235, 242, 244, 251, 270, 277

Offset: 1

Vladimir Joseph Stephan Orlovsky, Sep 13 2009

nonn

The values of A077116, sorted and duplicates removed.
Note that the values have been generated with a finite search radius and are not proved to be complete. [R. J. Mathar, Oct 09 2009]
Except for the leading 0, a subsequence of A229618 which is in turn (except for the initial 1) a subsequence of A106265.  The values {15, 18, 25, 44, 54, 61, 71, 72, 87, 106, 112, 118, 126, 127,...} are in  A229618 but not in the present sequence. Using results from A179386, it should be possible to prove that the sequence is complete up to a given point. - M. F. Hasler, Sep 26 2013

			The gap 0 appears in 1^3-1^2 or 4^3-8^2 etc.
The gap 2 appears for example in 3^3-5^2.
The gap 4 appears for example in 2^3-2^2 or 5^3-11^2.
The gap 19 appears in 7^3-18^2, the gap 20 in 6^3-14^2.

Essentially the same as A087285.

lst={};Do[a=n^3-Floor[Sqrt[n^3]]^2;If[a<=508,AppendTo[lst,a]],{n,2*8!}]; Take[Union@lst,90]

Edited by R. J. Mathar, Oct 09 2009

Name corrected by M. F. Hasler, Oct 05 2013

A229618 Numbers that are the distance between a square and the next larger cube.

Original entry on oeis.org

1, 2, 4, 7, 11, 13, 15, 18, 19, 20, 25, 26, 28, 35, 39, 40, 44, 45, 47, 48, 49, 53, 54, 55, 56, 60, 61, 63, 67, 71, 72, 74, 76, 79, 81, 83, 87, 100, 104, 106, 107, 109, 112, 116, 118, 126, 127, 128, 135, 139, 143

Offset: 1

M. F. Hasler, Sep 26 2013

This is the range of the sequence A181138 (= least k>0 such that n^2+k is a cube). Note that this is not the same as A087285 = range of A077116 = difference between a cube and the next smaller square: If n^2+k = y^3 is the smallest cube above n^2, then n^2 is not necessarily the largest square below y^3, e.g., 9+18 = 27 = 3^3 is the least cube above 9 = 3^2, but 25 = 5^2 is the largest square below 27. Therefore the number 18 is in this sequence, but not in A087285.
See A077116 and A181138 and A179386 for motivations.
Apart from the leading 1, this is a subsequence of A106265, which does not require the square to be the next smaller one: For example, 23 = 27 - 4 = 3^3 - 2^2 is in A106265 but not in this sequence. A165288 is a subsequence of this one, except for the initial term.

			a(1) = 1 = 1^3-0^2 (but this is the only solution to y^3-x^2 = 1).
a(2) = 2 = 27-25 (= 3^3-5^2), and this is the only solution to y^3-x^2 = 2.
The number 3 is not in the sequence since there are no x, y > 0 such that y^3-x^2 = 3.
a(3) = 4 = 8-4 (= 2^3-2^2) = 125-121 (= 5^3-11^2); these are the only two solutions to y^3-x^2 = 4, for all x>11, the minimal positive y^3-x^2 is 7.

Cf. A087285, A087286, A088017, A081121, A081120, A077116, A065733.

A179174 Numbers n such that Mordell's equation y^2 = x^3 - n has exactly 22 integral solutions.

Original entry on oeis.org

3807, 3896, 52784, 129556, 157239, 167600, 185112, 200871, 281439, 314199, 347967, 370647, 399375, 553648, 623872, 720703, 815728, 819775, 856799, 934975, 994816

Offset: 1

Artur Jasinski, Jun 30 2010

Counting (+x,+y) and (+x,-y) iff y != 0.

J. Gebel, Integer points on Mordell curves [Cached copy, after the original web site tnt.math.se.tmu.ac.jp was shut down in 2017]
Jose Aranda, C++ Program

Subsequence of A007412.

Cf. A081120, A081121, A179163-A179175, A134107, A106265.

Edited by Ray Chandler, Jul 11 2010

a(3)-a(21) from Jose Aranda, Aug 10 2024

A282093 Larger member of a pair (x,y) which solves x^2+y^2 = z^3 for positive x, y and z.

Original entry on oeis.org

2, 10, 11, 16, 26, 30, 39, 46, 52, 54, 68, 80, 88, 100, 110, 117, 120, 128, 130, 142, 145, 170, 198, 205, 208, 222, 236, 240, 250, 270, 286, 297, 310, 312, 322, 350, 366, 368, 371, 377, 406, 414, 415, 416, 432, 455, 481, 488, 505, 518, 520, 524, 544, 549, 584

Offset: 1

R. J. Mathar, Feb 06 2017

nonn

Values y such that x^2+y^2 = z^3 has a solution 1<=x<=y with integer x, y and z.
The positive values of A033431 are a subsequence, induced by solutions where x=y.
There are entries which have more than one representation, e.g., 10^2 + 198^2 = 34^3 and 107^2 + 198^2 = 37^3 both with y=198. 234^2 + 415^2 = 61^3 and 320^2 + 415^2 = 65^3 both with y=415.
The ordered sequence of x can apparently be constructed by retrieving the perfect squares in A106265 and printing their square roots: 1, 2, 5, 7, 8, 9, 10, 11, 16, 17, 18 , 26, 27, 30,...

			2^2+2^2=2^3, so 2 is in. 5^2+10^2=5^3, so 10 is in. 2^2+11^2 = 5^3, so 11 is in. 16^2+16^2=8^3, so 16 is in.

Cf. A000404 (values of z), A033431, A106265.

isA282093 := proc(y)
    local x,z3 ;
    for x from 1 to y do
        z3 := x^2+y^2 ;
        if isA000578(z3) then
            return true ;
        end if;
    end do:
    return false ;
end proc:
for y from 1 to 800 do
    if isA282093(y) then
        printf("%d,\n",y) ;
    end if;
end do:

isA282093[y_] := Module[{x, z3},
For[x = 1, x <= y, x++, z3 = x^2+y^2; If[IntegerQ[z3^(1/3)], Return[True]]]; Return[False]];
Reap[For[y = 1, y <= 800, y++, If[isA282093[y], Print[y]; Sow[y]]]][[2, 1]] (* Jean-François Alcover, May 29 2023, after R. J. Mathar *)

cp's OEIS Frontend

A106266 Least b such that A106265(n) + b^2 = c^3 for some c (given in A106267).

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A106267 Least c such that A106265(n) + b^2 = c^3 for some b (given in A106266).

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A081121 Numbers k such that Mordell's equation y^2 = x^3 - k has no integral solutions.

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A179388 Values y for records of minima of positive distances d = A179386(n) = A154333(x) = x^3 - y^2.

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A050801 Numbers k such that k^2 is expressible as the sum of two positive cubes in at least one way.

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A050802 Squares expressible as the sum of two positive cubes in at least one way.

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A165288 Possible values of the difference between a cube and the largest square not larger than the cube.

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