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%I A107364 #30 Sep 08 2022 08:45:18
%S A107364 1,3,9,13,27,39,81,117,169,243,351,507,729,1053,1521,2187,2197,3159,
%T A107364 4563,6561,6591,9477,13689,19683,19773,28431,28561,41067,59049,59319,
%U A107364 85293,85683,123201,177147,177957,255879,257049,369603,371293,531441
%N A107364 Numbers of the form (3^i)*(13^j).
%H A107364 Amiram Eldar, <a href="/A107364/b107364.txt">Table of n, a(n) for n = 1..10000</a>
%F A107364 Sum_{n>=1} 1/a(n) = (3*13)/((3-1)*(13-1)) = 13/8. - _Amiram Eldar_, Sep 23 2020
%F A107364 a(n) ~ exp(sqrt(2*log(3)*log(13)*n)) / sqrt(39). - _Vaclav Kotesovec_, Sep 23 2020
%t A107364 mx = 540000; Sort@ Flatten@ Table[3^i*13^j, {i, 0, Log[3, mx]}, {j, 0, Log[13, mx/3^i]}] (* _Robert G. Wilson v_, Aug 17 2012 *)
%t A107364 fQ[n_]:=PowerMod[39, n, n] == 0; Select[Range[2 10^7], fQ] (* _Vincenzo Librandi_, Jun 27 2016 *)
%o A107364 (PARI) list(lim)=my(v=List(),N);for(n=0,log(lim)\log(13),N=13^n;while(N<=lim,listput(v,N);N*=3));vecsort(Vec(v)) \\ _Charles R Greathouse IV_, Jun 28 2011
%o A107364 (Magma) [n: n in [1..10^7] | PrimeDivisors(n) subset [3, 13]]; // _Vincenzo Librandi_, Jun 27 2016
%Y A107364 Cf. A003586, A003592, A003593, A003591, A003594, A003595, A003596, A003597, A003598, A003599, A107326.
%K A107364 nonn,easy
%O A107364 1,2
%A A107364 Douglas Winston (douglas.winston(AT)srupc.com), May 23 2005

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