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A056828
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Numbers that are not the sum of at most three powerful (1) numbers.
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3
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OFFSET
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1,1
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COMMENTS
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Mollin and Walsh conjectured that there are no further terms.
Heath-Brown proved that the sequence is finite.
No other terms less than 40000000. - Paul.Jobling(AT)WhiteCross.com, May 14 2001
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REFERENCES
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Heath-Brown, D. R. "Ternary Quadratic Forms and Sums of Three Square-Full Numbers." In Seminaire de Theorie des Nombres, Paris 1986-87 (Ed. C. Goldstein). Boston, MA: Birkhauser, pp. 137-163, 1988.
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LINKS
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Table of n, a(n) for n=1..6.
R. A. Mollin and P. G. Walsh, On Powerful Numbers, Intern. J. Math. and Math. Sci, 9:801-806, 1986.
Eric Weisstein's World of Mathematics, Powerful Number.
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EXAMPLE
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Smallest powerful numbers are 1, 4, 8, 9, 16, 25,... so 7, 15 and 23 are not the sum of one, two or three of them.
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CROSSREFS
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Cf. A001694, A076871.
Sequence in context: A177768 A243582 A336819 * A113505 A184920 A076796
Adjacent sequences: A056825 A056826 A056827 * A056829 A056830 A056831
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KEYWORD
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fini,nonn
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AUTHOR
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Henry Bottomley, Aug 30 2000
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STATUS
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approved
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