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Search: id:A108145
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| A108145 |
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Smallest prime consisting of n successive positive integers in descending order followed by a 9. a(3k) = 0 as no such prime exists. |
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+0
8
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| 19, 439, 0, 262524239, 765439, 0, 109876549, 1098765439, 0, 504948474645444342419, 27262524232221201918179, 0, 2019181716151413121110989, 64636261605958575655545352519, 0
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(2) = 439, two successive positive integers 4,3 in descending order followed by a 9.
a(4) = 262524239 four successive positive integers 26,25,24,23 in descending order followed by a 9.
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MATHEMATICA
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a[n_]:=If[Mod[n, 3]==0, 0, (For[m=1, (v={}; Do[v=Join[v, IntegerDigits[k]], {k, m+n-1, m, -1}]); !PrimeQ[10FromDigits[v]+9], m++ ]; 10FromDigits[v]+9)]; Table[a[n], {n, 16}] - Farideh Firoozbakht.
f[n_] := Block[{t = Reverse@Range@n}, If[ Mod[n, 3] == 0, 0, While[p = FromDigits@Flatten@IntegerDigits@Join[t, {9}]; !PrimeQ@p, t++ ]; p]]; Array[f, 16] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A114754, A114755, A114756, A114757, A114758, A114759, A112716.
Sequence in context: A077716 A089573 A121938 this_sequence A114350 A012506 A081686
Adjacent sequences: A108142 A108143 A108144 this_sequence A108146 A108147 A108148
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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), Jan 01 2006
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EXTENSIONS
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Extended by Robert G. Wilson v (rgwv(at)rgwv.com), Ray Chandler (rayjchandler(AT)sbcglobal.net) and Farideh Firoozbakht (f.firoozbakht(AT)math.ui.ac.ir), Jan 02 2006
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