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Search: id:A080440
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| A080440 |
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a(1) = 13, a(n) = smallest prime obtained by inserting digits between every pair of digits of a(n-1). |
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+0
4
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| 13, 103, 10093, 100000963, 10000000000092653, 100000000000000000000000902060523, 10000000000000000000000000000000000000000000000090002000600051233
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Conjecture: Only one digit needs to be inserted between each pair of digit of a(n-1) to get a(n); i.e. a(n) contains exactly 2n-1 digits for n > 1.
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MATHEMATICA
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a[n_] := Block[{d = IntegerDigits[n]}, k = Length[d]; While[k > 1, d = Insert[d, 0, k]; k-- ]; d = FromDigits[d]; e = d; k = 0; While[ !PrimeQ[e], k++; e = d + 10FromDigits[ IntegerDigits[k], 100]]; e]; NestList[a, 13, 6]
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CROSSREFS
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Cf. A080439, A080441, A080442, A080883 - A080914.
Adjacent sequences: A080437 A080438 A080439 this_sequence A080441 A080442 A080443
Sequence in context: A066034 A100277 A087398 this_sequence A129762 A023011 A022641
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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), Feb 22 2003
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EXTENSIONS
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Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 22 2003
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