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 A156236 Smallest pentagonal number with n distinct prime factors. 3
 5, 12, 70, 210, 11310, 145860, 1560090, 23130030, 2491434660, 200736225690, 1906748513670, 281993526895080, 9427390580377770, 904832960818356570, 117584828859645537390, 2928413909631253063020, 400579656276180828206760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(18) <= 44573764536301609937057730. - Donovan Johnson, Feb 15 2012 LINKS Eric Weisstein's World of Mathematics, Pentagonal Numbers. EXAMPLE a(9) = 2491434660 = 2^2*3*5*11*13*17*19*29*31. 2491434660 is the smallest pentagonal number with 9 distinct prime factors. CROSSREFS Cf. A000326, A076551, A156237, A156238, A156239. Sequence in context: A207821 A297644 A242043 * A209481 A209340 A128323 Adjacent sequences:  A156233 A156234 A156235 * A156237 A156238 A156239 KEYWORD nonn AUTHOR Donovan Johnson, Feb 07 2009 EXTENSIONS a(17) from Donovan Johnson, Jun 26 2011 STATUS approved

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Last modified September 23 19:41 EDT 2020. Contains 337315 sequences. (Running on oeis4.)