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A219363
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Numbers such that the product of divisors of n is divisible by the product of divisors of sigma(n).
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1
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1, 37200, 86800, 170688, 260400, 334800, 2269200, 2343600, 2864400, 3385200, 4947600, 5291328, 5294800, 10155600, 11048400, 15884400, 18897600, 20422800, 30466800, 33070800, 44094400, 44528400, 61618368, 77338800, 91660800
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OFFSET
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1,2
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COMMENTS
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That is, numbers such that A007955(A000203(n)) | A007955(n).
F. Luca proved that this sequence is infinite.
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LINKS
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Table of n, a(n) for n=1..25.
F. Luca, On the product of divisors of n and sigma(n), J. Inequal. Pure Appl. Math., Volume 4, Issue 2, Article 46, 2003.
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MATHEMATICA
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Select[Range[1000000], Mod[Times @@ Divisors[#], Times @@ Divisors[DivisorSigma[1, #]]] == 0 &] (* T. D. Noe, Nov 19 2012 *)
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PROG
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(PARI) A007955(n)=if(issquare(n, &n), n^numdiv(n^2), n^(numdiv(n)/2))
is(n)=A007955(n)%A007955(sigma(n))==0 \\ Charles R Greathouse IV, Feb 04 2013
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CROSSREFS
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Cf. A000203, A007955.
Sequence in context: A279862 A112728 A250882 * A254564 A151630 A252166
Adjacent sequences: A219360 A219361 A219362 * A219364 A219365 A219366
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KEYWORD
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nonn
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AUTHOR
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Michel Marcus, Nov 19 2012
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STATUS
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approved
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