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Apr 27, 2019 at 12:35 comment added Freddy Barrera @FrançoisBrunault: I can confirm that there are no other perfect 2-runs and 3-runs below $1.8\times 10^{10}$, nor any perfect 4-runs. The closest for the latter is the run beginning at 113393279 that falls short by 4 of being perfect.
Apr 25, 2019 at 19:53 comment added François Brunault My computer checked that there is no other perfect 2-run below $10^{10}$. An observation: in all the known perfect runs, the largest number is a large prime times some small prime factors. I don't know if this could help to find more runs.
Apr 25, 2019 at 16:15 comment added Sylvain JULIEN Probably coincidental but your examples all fulfill $\tau(n)=2^m.d$ with $d$ a divisor of a prime.
Apr 25, 2019 at 14:09 history edited Freddy Barrera CC BY-SA 4.0
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Apr 24, 2019 at 19:28 comment added Freddy Barrera @GerhardPaseman: Yes, the above two examples, together with OP's (672, 673), are the only 2 and 3-runs below $10^8$.
Apr 24, 2019 at 18:24 comment added Gerhard Paseman Are these the only examples below 6 million? Gerhard "Is Keeper Of Imperfect Information" Paseman, 2019.04.24.
Apr 24, 2019 at 17:49 history answered Freddy Barrera CC BY-SA 4.0