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 A070009 Least number m such that the arithmetic mean of the distinct prime divisors of m is equal to 2^n. 2
 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, 44023413103, 40802188951 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Are there any terms with more than 3 prime factors? - David Wasserman, May 05 2003 LINKS Table of n, a(n) for n=1..30. FORMULA a(n) = Min{x; A008472(x)/A001221(x)=2^n}. EXAMPLE a(15) = 589794 because m = 2*3*98299; mean = (2+3+98299)/3 = 32768 = 2^15. MATHEMATICA 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 CROSSREFS Cf. A070005, A070006, A070007, A070008, A070009, A008472, A001414, A001221. Sequence in context: A295367 A214541 A180223 * A070170 A033568 A200156 Adjacent sequences: A070006 A070007 A070008 * A070010 A070011 A070012 KEYWORD nonn AUTHOR Labos Elemer, Apr 11 2002 EXTENSIONS Edited and extended by Robert G. Wilson v, Apr 30 2002 More terms from David Wasserman, May 05 2003 a(29)-a(30) from Donovan Johnson, Aug 06 2012 STATUS approved

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Last modified August 14 18:55 EDT 2024. Contains 375166 sequences. (Running on oeis4.)