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Search: id:A080442
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| A080442 |
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a(1) = 19, 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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| 19, 109, 10009, 100000039, 10000000000002359, 100000000000000000000000002031519, 10000000000000000000000000000000000000000000000000002000301050179
(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, 19, 6]
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CROSSREFS
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Cf. A080439, A080440, A080441, A080883 - A080914.
Sequence in context: A118607 A144246 A158715 this_sequence A033655 A164604 A142370
Adjacent sequences: A080439 A080440 A080441 this_sequence A080443 A080444 A080445
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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 and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 22 2003
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