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A152562
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Smallest number m such that sigma(m) has exactly n distinct prime factors.
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0
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2, 5, 20, 104, 936, 13842, 188424, 3249576, 81239400, 2388809736, 59720243400
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OFFSET
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1,1
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COMMENTS
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a(12) <= 2571228006912,
a(13) <= 85266458294400,
a(14) <= 4638227848902900,
a(15) <= 209103527633041800,
a(16) <= 10931190635671518600,
a(17) <= 545209768960172964900,
a(18) <= 34893425213451069753600,
a(19) <= 2000640771807316185690000. (End)
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LINKS
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FORMULA
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EXAMPLE
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a(9) = 81239400; sigma(81239400) = 300690390 = 2*3*5*7*11*13*17*19*31 (9 distinct prime factors).
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PROG
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(PARI) v=vector(9); for(m=2, 81239400, n=omega(sigma(m)); if(v[n]==0, v[n]=m; print(n " " v[n]))) /* Donovan Johnson, Mar 31 2013 */
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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