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A143026
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Positive integers n such that the fourth power of the number of positive divisors of n equals n.
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0
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OFFSET
| 1,2
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COMMENTS
| 625=5^4, 6561=3^8, 4100625=(3^8)(5^4).
There are no more terms in the sequence.
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REFERENCES
| T. Andreescu, D. Andrica and Z. Feng, 104 Number Theory Problems (from the training of the USA IMO team), Birkhauser, Boston, 2007, Advanced problem # 19, pp.85,145,146.
Roozbeh Hazrat, Mathematica: A Problem-Centered Approach, Springer 2010, p. 39
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EXAMPLE
| 625 has 5 divisors (1,5,25,125 and 625) and 5^4 = 625.
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MATHEMATICA
| Select[Range[4200000], DivisorSigma[0, #]^4==#&] (* From Harvey P. Dale, Oct 17 2011 *)
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CROSSREFS
| Sequence in context: A046755 A016816 A046756 * A064781 A055868 A106321
Adjacent sequences: A143023 A143024 A143025 * A143027 A143028 A143029
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KEYWORD
| fini,nonn,full
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AUTHOR
| Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 11 2008
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EXTENSIONS
| Second reference added by Harvey P. Dale, Oct 17 2011
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