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Search: id:A069048
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| A069048 |
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Numbers n such that n is a concatenation of consecutive natural numbers, starting from 1, and n+1 is prime. |
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1
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| 12, 123456, 123456789101112131415161718192021222324252627282930, 123456789101112131415161718192021222324252627282930313233343536373839404142434, 445464748495051525354555657585960616263646566676869707172737475767778798081828
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Let n be a concatenation of consecutive natural numbers, starting from 1. Is n ever a prime number?
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EXAMPLE
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123456 is a concatenation, starting with 1, of consecutive natural numbers, and 123456 + 1 is prime.
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MATHEMATICA
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z = {1}; For[i = 2, i <= 100, i++, z = Flatten[Append[z, IntegerDigits[i]]]; y = FromDigits[z]; If[PrimeQ[y + 1], Print[y]]]
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CROSSREFS
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Adjacent sequences: A069045 A069046 A069047 this_sequence A069049 A069050 A069051
Sequence in context: A051368 A103482 A056540 this_sequence A100246 A055323 A013796
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KEYWORD
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base,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Apr 03 2002
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