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A230564 Rational rank of the n-th taxicab elliptic curve x^3 + y^3 = A011541(n). 1
0, 2, 4, 5, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Guy, 2004: "Andrew Bremner has computed the rational rank of the elliptic curve x^3 + y^3 = Taxicab(n) as equal to 2, 4, 5, 4 for n = 2, 3, 4, 5, respectively."

Abhinav Kumar computed that a(1) = 0 (see the MathOverflow link for details). But Euler and Legendre scooped him (see the next comment).

Noam D. Elkies: "... the fact that x^3+y^3=2 has no [rational] solutions other than x=y=1 is attributed by Dickson to Euler himself: see Dickson's History of the Theory of Numbers (1920) Vol.II, Chapter XXI "Numbers the Sum of Two Rational Cubes", page 572. The reference (footnote 182) is "Algebra, 2, 170, Art. 247; French transl., 2, 1774, pp. 355-60; Opera Omnia, (1), I, 491". In the next page Dickson also refers to work of Legendre that includes this result (footnote 184: "Théorie des nombres, Paris, 1798, 409; ...")." See the MathOverflow link for further comments from Elkies.

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, 3rd edition, D1.

LINKS

Table of n, a(n) for n=1..5.

MathOverflow, What is the rational rank of the elliptic curve x^3 + y^3 = 2?, Oct 25 2013.

J. Silverman, Taxicabs and sums of two cubes, Amer. Math. Monthly, 100 (1993), 331-340.

FORMULA

a(n) = A060838(A011541(n)).

EXAMPLE

rank(x^3 + y^3 = 2) = 0.

rank(x^3 + y^3 = 1729) = 2.

rank(x^3 + y^3 = 87539319) = 4.

rank(x^3 + y^3 = 6963472309248) = 5.

rank(x^3 + y^3 = 48988659276962496) = 4.

CROSSREFS

Cf. A011541, A060838, A080642.

Sequence in context: A245816 A118461 A266408 * A011174 A123545 A123546

Adjacent sequences:  A230561 A230562 A230563 * A230565 A230566 A230567

KEYWORD

hard,more,nonn

AUTHOR

Jonathan Sondow, Oct 25 2013

STATUS

approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)