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A291829 Numbers k such that k^3 is the sum of two positive 7th powers. 0
32, 4096, 69984, 524288, 2500000, 8957952, 26353376, 67108864, 153055008, 320000000, 623589472, 1146617856, 2007952544, 3373232128, 5467500000, 8589934592, 13130837536, 19591041024, 28603895648, 35723051649, 40960000000, 57634833312, 79819452416, 108954414304 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

When a^7 + b^7 = m, (m^2*a)^7 + (m^2*b)^7 = m^15 is a cube.

When k in this sequence, k*(n^7) (n = 2, 3, ... ) is also in this sequence.

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

32^3 = 4^7 + 4^7, so 32 is in the sequence.

35723051649^3 = 16641^7 + 33282^7, so 35723051649 is in the sequence.

MATHEMATICA

lst={}; Do[If[IntegerQ[(n^3-a^7)^(1/7)], AppendTo[lst, n]], {n, 1.467*10^11}, {a, (n^3/2)^(1/7)}]; lst

CROSSREFS

Cf. A000578, A001015, A000404, A009003, A050801.

Sequence in context: A264126 A304401 A328275 * A248075 A248000 A278302

Adjacent sequences:  A291826 A291827 A291828 * A291830 A291831 A291832

KEYWORD

nonn

AUTHOR

XU Pingya, Sep 03 2017

STATUS

approved

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Last modified September 21 13:58 EDT 2021. Contains 347598 sequences. (Running on oeis4.)