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A114228
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Smallest number k (k>=1) that makes the n-th prime prime[n] plus 2*prime[k] a prime.
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6
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1, 2, 1, 2, 1, 2, 1, 2, 4, 2, 1, 2, 1, 2, 2, 4, 2, 1, 6, 2, 1, 2, 4, 1, 2, 1, 2, 1, 4, 1, 2, 4, 3, 4, 2, 2, 1, 2, 2, 4, 3, 2, 1, 4, 7, 5, 1, 2, 1, 2, 8, 3, 2, 2, 2, 4, 2, 1, 6, 3, 4, 1, 2, 1, 4, 2, 3, 2, 1, 2, 4, 2, 2, 1, 2, 12, 1, 8, 3, 4, 3, 6, 2, 1, 2, 4, 1, 2, 1, 12, 11, 1, 14, 1, 2, 4, 6, 7, 2, 3, 2, 2, 8
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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EXAMPLE
| Prime[2]=3, 3+2*Prime[1]=7 is prime, so k[2]=1;
Prime[3]=5, 5+2*Prime[2]=11 is prime, so k[3]=2;
...
Prime[20]=71, 71+2*Prime[6]=97 is prime, so k[20]=6
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MATHEMATICA
| Table[p1 = Prime[n1]; n2 = 1; p2 = 2; While[ cp = p1 + 2*p2; ! PrimeQ[cp], n2++; p2 = Prime[n2]]; n2, {n1, 2, 201}]
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CROSSREFS
| Cf. A114227.
Sequence in context: A161273 A160977 A030738 * A168580 A060938 A119647
Adjacent sequences: A114225 A114226 A114227 * A114229 A114230 A114231
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KEYWORD
| easy,nonn
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AUTHOR
| Lei Zhou (lzhou5(AT)emory.edu), Nov 18 2005
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