A356708 - OEIS

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A356708

Number of integral solutions to Mordell's equation y^2 = x^3 + n^3 with y nonnegative.

3, 4, 1, 3, 1, 1, 2, 5, 3, 3, 2, 1, 1, 3, 1, 3, 1, 4, 1, 1, 2, 2, 2, 1, 3, 2, 1, 3, 1, 1, 1, 5, 3, 2, 2, 3, 3, 2, 1, 3, 1, 1, 1, 2, 1, 2, 1, 1, 3, 4, 1, 1, 1, 1, 1, 4, 4, 1, 1, 1, 1, 1, 2, 3, 9, 1, 1, 1, 1, 3, 2, 5, 1, 2, 1, 1, 1, 5, 1, 1, 3, 1, 1, 3, 1, 2, 1, 3, 1, 3, 3, 2, 1, 1, 2, 1, 1, 4, 2, 3

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OFFSET

1,1

COMMENTS

Equivalently, number of different values of x in the integral solutions to the Mordell's equation y^2 = x^3 + n^3.

LINKS

Table of n, a(n) for n=1..100.

FORMULA

a(n) = (A081119(n^3)+1)/2 = A134108(n^3) = (A356706(n)+1)/2 = A356707(n)+1.

EXAMPLE

a(2) = 4 because the solutions to y^2 = x^3 + 2^3 with y >= 0 are (-2,0), (1,3), (2,4), and (46,312).

PROG

(SageMath) [(len(EllipticCurve(QQ, [0, n^3]).integral_points(both_signs=True))+1)/2 for n in range(1, 61)] # Lucas A. Brown, Sep 04 2022

CROSSREFS

Cf. A081119, A134108, A356706, A356707.

Indices of 1, 2, 3, and 4: A356709, A356710, A356711, A356712.

Sequence in context: A021297 A124909 A348354 * A281098 A090279 A101667

Adjacent sequences: A356705 A356706 A356707 * A356709 A356710 A356711

KEYWORD

nonn,hard

AUTHOR

Jianing Song, Aug 23 2022

EXTENSIONS

a(21) corrected and a(22)-a(60) by Lucas A. Brown, Sep 04 2022

a(61)-a(100) from Max Alekseyev, Jun 01 2023

STATUS

approved