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 A143026 Positive integers n such that the fourth power of the number of positive divisors of n equals n. 1
 1, 625, 6561, 4100625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 625=5^4, 6561=3^8, 4100625=(3^8)(5^4). There are no more terms in the sequence. 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 LINKS EXAMPLE 625 has 5 divisors (1, 5, 25, 125 and 625) and 5^4 = 625. MATHEMATICA Select[Range[4200000], DivisorSigma[0, #]^4==#&] (* Harvey P. Dale, Oct 17 2011 *) CROSSREFS Cf. A066693. Sequence in context: A046755 A016816 A046756 * A238700 A064781 A250832 Adjacent sequences:  A143023 A143024 A143025 * A143027 A143028 A143029 KEYWORD fini,nonn,full AUTHOR Emeric Deutsch, Aug 11 2008 EXTENSIONS Second reference added by Harvey P. Dale, Oct 17 2011 STATUS approved

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Last modified August 10 12:19 EDT 2020. Contains 336379 sequences. (Running on oeis4.)