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A165497
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a(n) starts arithmetic progression of n terms separated by tau(a(n)), each term having the same number of divisors
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2
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1, 3, 3, 60, 60, 201, 481, 5989, 3122037, 4434429, 13576837, 183894465, 187925171, 209072257, 1498642520, 12239200420, 20220712468, 20220712468, 875023683404, 992997544772, 2721798771116, 9770941874212, 9770941874212
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OFFSET
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1,2
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COMMENTS
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a(15) > 10^9.
a(19) > 10^11. - Donovan Johnson, Sep 24 2009
a(24) > 10^13. - Giovanni Resta, Aug 02 2013
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LINKS
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Table of n, a(n) for n=1..23.
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EXAMPLE
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tau(60) = tau(72) = tau(84) = tau(96) = tau(108) = 12. This is the first such progression of length greater than 3, so a(4) and a(5) are both 60.
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PROG
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(PARI) has(n)=my(t=numdiv(n), s=1); while(numdiv(n+=t)==t, s++); s
a(n)=my(k); while(has(k++)<n, ); k \\ Charles R Greathouse IV, Apr 24 2015
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CROSSREFS
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Cf. A064491, A165498, A165499.
Sequence in context: A290567 A100065 A066807 * A051752 A102065 A102074
Adjacent sequences: A165494 A165495 A165496 * A165498 A165499 A165500
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KEYWORD
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hard,nonn,more
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AUTHOR
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Hugo van der Sanden, Sep 21 2009
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EXTENSIONS
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a(15)-a(18) from Donovan Johnson, Sep 24 2009
a(19)-a(23) from Giovanni Resta, Aug 02 2013
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STATUS
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approved
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