%I A037057
%S A037057 2,223,2221,22229,1222229,20222227,22222223,222222227,20222222221,
%T A037057 22222222223,2122222222229,21222222222221,22222222222229,
%U A037057 222222222222227,21222222222222221,202222222222222229
%N A037057 Smallest prime containing exactly n 2's.
%t A037057 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, 2], {n, 1, 18}]
%Y A037057 Cf. A065585, A037056, A034388, A036507-A036536.
%Y A037057 Cf. A037053, A037055, A037059, A037061, A037063, A037065, A037067, A037069, 
               A037071.
%Y A037057 Sequence in context: A124188 A078276 A117076 this_sequence A132936 A110715 
               A071225
%Y A037057 Adjacent sequences: A037054 A037055 A037056 this_sequence A037058 A037059 
               A037060
%K A037057 nonn,base
%O A037057 1,1
%A A037057 Patrick De Geest (pdg(AT)worldofnumbers.com), Jan 04 1999.
%E A037057 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 
               23 2003