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Search: id:A068174
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| A068174 |
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Define an increasing sequence as follows. Start with an initial term, the seed (which need not have the property of the sequence); subsequent terms are obtained by inserting/placing at least one digit in the previous term to obtain the smallest number with the given property. Here the property is be a prime. |
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1
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| 9, 19, 109, 1009, 10009, 100019, 1000159, 10001569, 100001569, 1000015069, 10000135069, 100001350649, 1000013500649, 10000130500649, 100001303500649, 1000013032500649, 10000103032500649, 100001030325003649
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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The primes obtained by inserting/placing a digit in a(2) = 19 are 109, 139, 149, 179, 199 etc. and a(3)= 109 is the smallest.
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MATHEMATICA
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f[n_] := Block[{b = PadLeft[ IntegerDigits[n], Floor[ Log[10, n] + 1]], k = 0}, While[ !PrimeQ[ FromDigits[ Insert[b, k, -2]]], k++ ]; FromDigits[ Insert[b, k, -2]]]; NestList[ f, 9, 18]
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CROSSREFS
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Cf. A068166, A068167, A068169, A068170, A068171, A068172, A068173.
Sequence in context: A041158 A000981 A060227 this_sequence A041677 A041160 A089565
Adjacent sequences: A068171 A068172 A068173 this_sequence A068175 A068176 A068177
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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 25 2002
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EXTENSIONS
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Edited by njas and Robert G. Wilson v (rgwv(AT)rgwv.com), May 08 2002
Corrected and extended by Robert Gerbicz (gerbicz(AT)freemail.hu), Sep 06 2002
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