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Search: id:A112716
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| A112716 |
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Smallest prime of the form: n successive positive integers in descending order followed by a 7. |
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+0
8
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| 17, 547, 3217, 65437, 543217, 8765437, 76543217, 41403938373635347, 9876543217, 282726252423222120197, 1312111098765437, 2322212019181716151413127, 222120191817161514131211107, 1615141312111098765437
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(4) = 65437, four successive positive integers 6,5,4,3 in descending order followed by a 7.
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MATHEMATICA
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a[n_]:=(For[m=1, (v={}; Do[v=Join[v, IntegerDigits[k]], {k, m+n-1, m, -1}]); !PrimeQ[10FromDigits[v]+7], m++ ]; 10FromDigits[v]+7); Table[a[n], {n, 14}] - Farideh Firoozbakht
f[n_] := Block[{t = Reverse@Range@n}, While[p = FromDigits@Flatten@IntegerDigits@Join[t, {7}]; !PrimeQ@p, t++ ]; p]; Array[f, 14] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A114754, A114755, A114756, A114757, A114758, A114759, A108145.
Sequence in context: A012792 A012232 A114063 this_sequence A012069 A056771 A041547
Adjacent sequences: A112713 A112714 A112715 this_sequence A112717 A112718 A112719
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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 (mymontain(AT)yahoo.com), Jan 02 2006
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