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A189394
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Highly composite numbers whose number of divisors is also a highly composite number.
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0
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1, 2, 6, 12, 60, 360, 1260, 2520, 5040, 55440, 277200, 720720, 3603600, 61261200, 220540320, 293318625600, 6746328388800, 195643523275200
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OFFSET
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1,2
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COMMENTS
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Both n and d(n) are highly composite numbers.
It is extremely likely that this sequence is complete. The highly composite numbers have a very special form. The number of divisors of a large HCN has a high power of 2 in its factorization -- which is not the form of an HCN. - T. D. Noe, Apr 21 2011
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LINKS
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Table of n, a(n) for n=1..18.
A. Flammenkamp, Highly composite numbers
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EXAMPLE
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d(60) = 12; both 60 and 12 are highly composite numbers
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MATHEMATICA
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(* First run program at A002182 *) Select[A002182, MemberQ[A002182, DivisorSigma[0, #]] &] (* From Alonso del Arte, Apr 21 2011 *)
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CROSSREFS
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Cf. A002182, A002183, A141320.
Sequence in context: A220027 A072489 A072487 * A182862 A072938 A160274
Adjacent sequences: A189391 A189392 A189393 * A189395 A189396 A189397
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KEYWORD
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nonn,more
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AUTHOR
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Krzysztof Ostrowski, Apr 21 2011
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STATUS
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approved
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