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A104873
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Concatenations of pairs of primes that differ by 10^12.
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611000000000061, 1631000000000163, 1931000000000193, 2111000000000211, 2711000000000271, 3311000000000331, 5471000000000547, 6611000000000661, 7511000000000751, 7871000000000787, 9971000000000997, 10511000000001051
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Integers in this sequence can never be prime, as they are all multiples of 3. They can be semiprimes, as is the case for Prime(177) concatenated with Prime(37607912056) = 10511000000001051 = 3 * 3503666666667017.
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FORMULA
| a(n) = Concatenate(P, P+10^12) iff P prime and P+10^12 prime.
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EXAMPLE
| 61 is prime, specifically prime(18) and 61 + 10^12 is prime, specifically prime(7607912020), so their concatenation is in this sequence: 611000000000061. The concatenation is not itself prime, as it equals 3 * 7 * 23 * 1265010351967.
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CROSSREFS
| Cf. A000040, A001358, A023201, A100750, A103195, A103206, A104718, A104719, A103523, A103534, A103576, A103617.
Sequence in context: A172665 A172601 A086438 * A172585 A088867 A159042
Adjacent sequences: A104870 A104871 A104872 * A104874 A104875 A104876
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KEYWORD
| base,easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Mar 29 2005
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