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A037063 Smallest prime containing exactly n 5's. 14
5, 557, 5557, 155557, 555557, 15555557, 55555553, 3555555551, 5555555557, 525555555557, 555555555551, 5555555555551, 355555555555559, 555555555555557, 51555555555555551, 545555555555555551 (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, 5], {n, 1, 18}]

CROSSREFS

Cf. A065588, A037062, A034388, A036507-A036536.

Cf. A037053, A037055, A037057, A037059, A037061, A037065, A037067, A037069, A037071.

Sequence in context: A110721 A067446 A112900 * A153404 A185555 A093941

Adjacent sequences:  A037060 A037061 A037062 * A037064 A037065 A037066

KEYWORD

nonn,base

AUTHOR

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

EXTENSIONS

More terms from Randall Rathbun, Jan 11 2002

Edited and corrected by Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 04 2003

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Last modified February 15 10:28 EST 2012. Contains 205763 sequences.