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A089365
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Smallest prime whose product of digits is 2^n.
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7
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11, 2, 41, 181, 281, 1481, 881, 4481, 18481, 48281, 48481, 228881, 284881, 828881, 884881, 4448881, 4848881, 18848881, 24888881, 48888841, 88884881, 188888881, 888828881, 848888881, 4848488881, 4488888881, 18848888881, 28888884881
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OFFSET
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0,1
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LINKS
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EXAMPLE
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a(8) = 24481 and the digital product is 2^8.
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MATHEMATICA
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NextPrim[n_] := Block[{k = n + 1}, While[ ! PrimeQ[k], k++ ]; k]; a = Table[0, {24}]; p = 2; Do[q = Log[2, Times @@ IntegerDigits[p]]; If[q != 0 && IntegerQ[q] && a[[q]] == 0, a[[q]] = p; Print[q, " = ", p]]; p = NextPrim[p], {n, 1, 10^9}] (* Robert G. Wilson v, Nov 08 2003 *)
For a(8): a = Map[ FromDigits, Join[{0}, #, {1}] & /@ Permutations[{2, 8, 8 }]]; Min[ Select[a, PrimeQ[ # ] & ]] (* Robert G. Wilson v, Nov 08 2003 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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