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Search: id:A114235
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| A114235 |
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n(k) is the largest prime which is smaller than Prime[k] and makes 2*Prime[k]+Prime[n] a prime. |
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+0
9
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| 3, 5, 7, 11, 13, 5, 13, 13, 17, 29, 31, 41, 43, 43, 31, 59, 59, 37, 53, 71, 73, 79, 89, 79, 101, 103, 89, 67, 113, 127, 127, 131, 103, 137, 149, 137, 157, 163, 163, 179, 181, 191, 193, 179, 197, 197, 223, 173, 211, 223, 227, 241, 229, 193, 223, 269, 269, 277, 263
(list; graph; listen)
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OFFSET
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3,1
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EXAMPLE
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k=3: 2*Prime[3]+3=2*5+3=13 is prime, so n(3)=3;
k=4: 2*Prime[4]+5=2*7+5=19 is prime, so n(4)=5;
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k=8: 2*Prime[8]+17=2*19+17=55 is not prime
2*Prime[8]+13=2*19+13=51 is not prime
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2*Prime[8]+5=2*19+5=43 is prime, so n(8)=5;
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MATHEMATICA
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Table[p1 = Prime[n1]; n2 = 1; p2 = Prime[n1 - n2]; While[cp = 2*p1 + p2; ! PrimeQ[cp], n2++; If[n2 ≥ n1, Print[n1]]; p2 = Prime[n1 - n2]]; p2, {n1, 3, 202}]
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CROSSREFS
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Cf. A114227, A114230, A073703.
Adjacent sequences: A114232 A114233 A114234 this_sequence A114236 A114237 A114238
Sequence in context: A066168 A109908 A102941 this_sequence A086527 A070087 A088828
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KEYWORD
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easy,nonn
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AUTHOR
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Lei Zhou (lzhou5(AT)emory.edu), Nov 20 2005
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