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A037057 Smallest prime containing exactly n 2's. 15
2, 223, 2221, 22229, 1222229, 20222227, 22222223, 222222227, 20222222221, 22222222223, 2122222222229, 21222222222221, 22222222222229, 222222222222227, 21222222222222221, 202222222222222229 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

MATHEMATICA

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}]

CROSSREFS

Cf. A065585, A037056, A034388, A036507-A036536.

Cf. A037053, A037055, A037059, A037061, A037063, A037065, A037067, A037069, A037071.

Sequence in context: A124188 A078276 A117076 * A132936 A110715 A071225

Adjacent sequences:  A037054 A037055 A037056 * A037058 A037059 A037060

KEYWORD

nonn,base

AUTHOR

Patrick De Geest (pdg(AT)worldofnumbers.com), Jan 04 1999.

EXTENSIONS

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 23 2003

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Last modified February 16 05:39 EST 2012. Contains 205860 sequences.