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A087242
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Smallest prime number p such that n+p = q is also a prime, or 0 if no such prime number exists.
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2
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2, 3, 2, 3, 2, 5, 0, 3, 2, 3, 2, 5, 0, 3, 2, 3, 2, 5, 0, 3, 2, 7, 0, 5, 0, 3, 2, 3, 2, 7, 0, 5, 0, 3, 2, 5, 0, 3, 2, 3, 2, 5, 0, 3, 2, 7, 0, 5, 0, 3, 2, 7, 0, 5, 0, 3, 2, 3, 2, 7, 0, 5, 0, 3, 2, 5, 0, 3, 2, 3, 2, 7, 0, 5, 0, 3, 2, 5, 0, 3, 2, 7, 0, 5, 0, 3, 2, 13, 0, 7, 0, 5, 0, 3, 2, 5, 0, 3, 2, 3, 2, 5, 0, 3, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| a(n)=Min{x; n+x is prime}
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EXAMPLE
| a(n)=0, i.e. no solution exists if n is a special prime, namely n is not a lesser-twin-prime;
e.g. if n=7, then neither 7+2=9 nor 7+(oddprime) is a prime, thus no p prime exits such that 7+p was also a prime.
If n=lesser-twin-prime then a(n)=2 is a solution because n+a[n]=n+2=larger-twin-prime satisfying condition.
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CROSSREFS
| Cf. A087243.
Sequence in context: A167530 A205789 A029208 * A123556 A053669 A112047
Adjacent sequences: A087239 A087240 A087241 * A087243 A087244 A087245
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Sep 04 2003
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