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A052080
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Concatenation of n consecutive descending numbers starting from a(n) produces the smallest possible prime of this form, O if no such prime exists.
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3
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2, 4, 0, 10, 7, 0, 73, 46, 0, 56, 219, 0, 25, 60, 0, 52, 117, 0, 535, 172, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| First hard cases occur for n = 22, 88 and 110.
a(22) = 10^1631+10 is found by James Merickel in Feb 2011.
a(88) = 10^14+6
a(110) = 10^19+26 is found by Chris Nash.
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LINKS
| C. Rivera, Prime Puzzle 78
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EXAMPLE
| For n = 8 we have a(8) = 46 so the eight consecutive descending numbers 46,45,44,43,42,41,40 and 39 concatenated together gives the smallest possible prime of this form, 4645444342414039.
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CROSSREFS
| Cf. A052077, A052078, A052079.
Sequence in context: A021419 A180192 A066529 * A073451 A078022 A203850
Adjacent sequences: A052077 A052078 A052079 * A052081 A052082 A052083
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KEYWORD
| nonn,base,hard
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AUTHOR
| Patrick De Geest (pdg(AT)worldofnumbers.com), Jan 15 2000.
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EXTENSIONS
| Terms a(7)-a(21) calculated by Carlos Rivera (crivera(AT)primepuzzles.net) and Felice Russo (frusso(AT)micron.com).
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