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A230563 Smallest number that is the sum of three positive n-th powers in at least two ways. 15
5, 27, 251, 2673, 1375298099, 160426514 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(7) > 10^26 (if it exists). - Donovan Johnson, Nov 22 2013
a(7) > 33055^7 ~ 4.31*10^31 (if it exists). Duncan Moore, Oct 07 2017
REFERENCES
G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, section 21.11.
LINKS
R. Alter, Computations and generalizations on a remark of Ramanujan, pp. 182-196 of "Analytic Number Theory (Philadelphia, 1980)", ed. M. I. Knopp, Lect. Notes Math., Vol. 899, 1981. The value for a(6) given in Table 5 is wrong.
EXAMPLE
5 = 1^1 + 1^1 + 3^1 = 1^1 + 2^1 + 2^1.
27 = 1^2 + 1^2 + 5^2 = 3^2 + 3^2 + 3^2.
251 = 1^3 + 5^3 + 5^3 = 2^3 + 3^3 + 6^3.
2673 = 2^4 + 4^4 + 7^4 = 3^4 + 6^4 + 6^4.
1375298099 = 3^5 + 54^5 + 62^5 = 24^5 + 28^5 + 67^5.
160426514 = 3^6 + 19^6 + 22^6 = 10^6 + 15^6 + 23^6.
CROSSREFS
Sequence in context: A167019 A356538 A342904 * A204266 A266204 A360770
KEYWORD
hard,more,nice,nonn
AUTHOR
Jonathan Sondow, Oct 25 2013
EXTENSIONS
a(4) and a(5) corrected by Donovan Johnson, Oct 28 2013
Edited by N. J. A. Sloane, Apr 03 2021
STATUS
approved

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Last modified March 29 11:45 EDT 2024. Contains 371278 sequences. (Running on oeis4.)