%I A037061
%S A037061 41,443,4441,44449,444443,24444443,424444441,444444443,4444444447,
%T A037061 44444444441,444444444443,14444444444449,440444444444441,
%U A037061 2444444444444447,44044444444444441,424444444444444447
%N A037061 Smallest prime containing exactly n 4's.
%t A037061 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, 4], {n, 1, 18}]
%Y A037061 Cf. A065587, A037060, A034388, A036507-A036536.
%Y A037061 Cf. A037053, A037055, A037057, A037059, A037063, A037065, A037067, A037069, 
               A037071.
%Y A037061 Sequence in context: A083761 A112748 A061643 this_sequence A103735 A166843 
               A098958
%Y A037061 Adjacent sequences: A037058 A037059 A037060 this_sequence A037062 A037063 
               A037064
%K A037061 nonn,base
%O A037061 1,1
%A A037061 Patrick De Geest (pdg(AT)worldofnumbers.com), Jan 04 1999.
%E A037061 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 
               23 2003