Search: id:A037071
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%I A037071
%S A037071 19,199,1999,49999,199999,2999999,19999999,799999999,9199999999,
%T A037071 59999999999,959999999999,9919999999999,59999999999999,499999999999999,
%U A037071 9299999999999999,99919999999999999,994999999999999999,9991999999999999999,
               29999999999999999999,989999999999999999999
%N A037071 Smallest prime containing exactly n 9's.
%t A037071 f[n_, b_] := Block[{k = 10^(n + 1), p = Permutations[ Join[ Table[b, 
               {i, 1, n}], {x}]], c = Complement[Table[j, {j, 0, 9}], {b}], q = 
               {}}, Do[q = Append[q, Replace[p, x -> c[[i]], 2]], {i, 1, 9}]; r 
               = Min[ Select[ FromDigits /@ Flatten[q, 1], PrimeQ[ # ] & ]]; If[r 
               ? Infinity, r, p = Permutations[ Join[ Table[ b, {i, 1, n}], {x, 
               y}]]; q = {}; Do[q = Append[q, Replace[p, {x -> c[[i]], y -> c[[j]]}, 
               2]], {i, 1, 9}, {j, 1, 9}]; Min[ Select[ FromDigits /@ Flatten[q, 
               1], PrimeQ[ # ] & ]]]]; Table[ f[n, 9], {n, 1, 20}]
%Y A037071 Cf. A065592, A065582, A037070, A034388, A036507-A036536.
%Y A037071 Cf. A037053, A037055, A037057, A037059, A037061, A037063, A037065, A037067, 
               A037069.
%Y A037071 Sequence in context: A147830 A135162 A067272 this_sequence A065582 A055558 
               A160452
%Y A037071 Adjacent sequences: A037068 A037069 A037070 this_sequence A037072 A037073 
               A037074
%K A037071 nonn,base
%O A037071 1,1
%A A037071 Patrick De Geest (pdg(AT)worldofnumbers.com), Jan 04 1999.
%E A037071 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 10 2002

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