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Search: id:A099070
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| A099070 |
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Numbers n such that the concatenation of all nonprime natural numbers up to n with decreasing order is prime. |
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+0
4
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OFFSET
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1,1
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COMMENT
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If n is in the sequence and n+1 is prime then n+1 is also in the sequence. Next term is greater than 5450 and the prime corresponding to the next term has more than 18000 digits. Number of digits of primes corresponding to the nine known terms of the sequence are respectively 2,2,3,3,4,5,29,5010 & 5010.
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LINKS
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C. Rivera, Primes by Listing.
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EXAMPLE
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9 is in the sequence because all nonprime natural numbers
up to 9 are 1,4,6,8 & 9 and 98641 is prime.
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MATHEMATICA
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Do[If[PrimeQ[(v={}; Do[If[ !PrimeQ[n+1-j], v=Join[v, IntegerDigits [n+1-j]]], {j, n}]; FromDigits[v])], Print[n]], {n, 5450}]
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CROSSREFS
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Cf. A046284, A099071.
Sequence in context: A161674 A109602 A084991 this_sequence A065342 A076597 A121541
Adjacent sequences: A099067 A099068 A099069 this_sequence A099071 A099072 A099073
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KEYWORD
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base,more,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), Nov 04 2004
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