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 A165497 a(n) starts arithmetic progression of n terms separated by tau(a(n)), each term having the same number of divisors 2
 1, 3, 3, 60, 60, 201, 481, 5989, 3122037, 4434429, 13576837, 183894465, 187925171, 209072257, 1498642520, 12239200420, 20220712468, 20220712468, 875023683404, 992997544772, 2721798771116, 9770941874212, 9770941874212 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(15) > 10^9. a(19) > 10^11. - Donovan Johnson, Sep 24 2009 a(24) > 10^13. - Giovanni Resta, Aug 02 2013 LINKS EXAMPLE 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. PROG (PARI) has(n)=my(t=numdiv(n), s=1); while(numdiv(n+=t)==t, s++); s a(n)=my(k); while(has(k++)

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Last modified May 8 15:28 EDT 2021. Contains 343666 sequences. (Running on oeis4.)