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COMMENTS
| Comment from Hans Havermann, Sep 26 2005:
"Noting that a(6) = a(5)*(10^2+1) and a(7) = a(5)*(10^4+1), we can
derive an upper bound for a(n), n>7, of 24024*(10^x+1), where x is
the smallest power that gives the number (10^x+1) exactly (n-5)
factors-greater-than-13. For n = {8, 9, 10, 11, 12, 13, 14, 15, 16},
this would be x = {10, 14, 16, 36, 30, 55, 45, 77, 70}. I think this
upper limit exists for all n, so a(n) always exists."
a(9) <= 2305213214304. a(10) <= 230316132350304. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 09 2010]
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MATHEMATICA
| r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[k = 1; While[r[k] == k || Length[Select[Divisors[k], PrimeQ]] != n || Select[Divisors[k], PrimeQ] != Select[Divisors[r[k]], PrimeQ], k++ ]; Print[k], {n, 2, 10}]
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