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A071852
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Smallest k such that 2^k+1 has exactly n distinct prime factors.
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0
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1, 5, 14, 18, 30, 42, 99, 114, 78, 90, 175, 150, 324, 210, 315, 234, 270, 585, 405, 765, 390, 450, 510
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n) = min (k : A046799(k) = n )
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MATHEMATICA
| For[n = 1, n < 15, n++, k := 1; While[Not[Length[FactorInteger[2^k + 1]] == n], k++ ]; Print[k]] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 09 2006
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PROG
| (PARI) for(n=1, 10, s=1; while(abs(omega(2^s+1)-n)>0, s++); print1(s, ", "))
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CROSSREFS
| Sequence in context: A196366 A053782 A102884 * A022139 A143707 A003248
Adjacent sequences: A071849 A071850 A071851 * A071853 A071854 A071855
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KEYWORD
| more,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 09 2002
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EXTENSIONS
| 175 and 150 from Erich Friedman (efriedma(AT)stetson.edu), Aug 08 2005
a(13)-a(23) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 22 2008
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