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Search: id:A070009
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| A070009 |
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Least number m such that arithmetical mean of distinct primes dividing m equals 2^n. |
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+0
2
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| 2, 15, 39, 87, 183, 2071, 1255, 1527, 3063, 18402, 12279, 106327, 49143, 622231, 589794, 1703767, 1310695, 9961111, 3145719, 31457210, 12582903, 310377127, 50331639, 2046816631, 335544295, 10603194271, 8858369762, 1610612727
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OFFSET
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1,1
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COMMENT
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a(21) = 12582903
Are there any terms with more than 3 prime factors? - David Wasserman (wasserma(AT)spawar.navy.mil), May 05 2003
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FORMULA
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a(n)=Min{x; A008472(x)/A001221(x)=2^n}
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EXAMPLE
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a(15) = 589794 because m = 2.3.98299; mean = (2+3+98299)/3 = 32768 = 2^15.
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MATHEMATICA
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a = Table[0, {21}]; Do[b = Transpose[ FactorInteger[n]][[1]]; c = Log[2, Apply[ Plus, b] / Length[b]]; If[ IntegerQ[c] && a[[c]] == 0, a[[c]] = n], {n, 2, 10^8/3}]; a
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CROSSREFS
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Cf. A070005-A070009, A008472, A001414, A001221.
Sequence in context: A075542 A064113 A007217 this_sequence A070170 A033568 A032016
Adjacent sequences: A070006 A070007 A070008 this_sequence A070010 A070011 A070012
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Apr 11 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 30 2002
More terms from David Wasserman (wasserma(AT)spawar.navy.mil), May 05 2003
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