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Search: id:A090872
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| A090872 |
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a(n) is the smallest number m greater than 1 such that m^(2^k)+1 for k=0,1,...,n are primes. |
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+0
5
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OFFSET
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0,1
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COMMENT
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The first five terms of this sequence correspond to Fermat primes.
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LINKS
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C. Rivera, Puzzle 137. Product of primes + 1, a square.
C. Rivera (ed.), Prime Puzzle # 399.
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EXAMPLE
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a(5)=7072833120 because 7072833120^2^k+1 for k=0,1,2,3,4,5 are primes.
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CROSSREFS
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Cf. A019434, A000215.
Cf. A090873-A090875.
Sequence in context: A056993 A057331 A067089 this_sequence A063473 A096859 A005086
Adjacent sequences: A090869 A090870 A090871 this_sequence A090873 A090874 A090875
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KEYWORD
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nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jan 31 2004
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EXTENSIONS
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a(6) from Jens Kruse Andersen (jens.k.a(AT)get2net.dk), May 06 2007
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