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Search: id:A089365
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| A089365 |
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Smallest prime whose product of digits is 2^n. |
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+0
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, 12888884881, 8888882881, 18848888881, 28888884881
(list; graph; listen)
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OFFSET
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0,1
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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}]
For a(8): a = Map[ FromDigits, Join[{0}, #, {1}] & /@ Permutations[{2, 8, 8 }]]; Min[ Select[a, PrimeQ[ # ] & ]] (both from Robert G. Wilson v, Nov 08 2003)
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CROSSREFS
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Cf. A088653, A090840, A091465, A090841, A089298.
Sequence in context: A077344 A095157 A110767 this_sequence A130217 A096044 A160464
Adjacent sequences: A089362 A089363 A089364 this_sequence A089366 A089367 A089368
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 07 2003
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EXTENSIONS
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Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 08 2003
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