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A114266
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a(n) is the minimal number m that makes 2*prime(n)+prime(n+m) a prime.
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2
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1, 1, 1, 3, 3, 1, 1, 1, 3, 1, 2, 4, 6, 2, 6, 2, 1, 2, 5, 5, 2, 1, 2, 3, 5, 3, 1, 6, 1, 1, 8, 2, 4, 7, 1, 9, 3, 2, 9, 7, 5, 10, 4, 5, 1, 5, 5, 1, 1, 1, 8, 1, 1, 4, 6, 2, 1, 2, 12, 10, 1, 11, 8, 3, 11, 2, 2, 1, 4, 1, 7, 2, 3, 2, 11, 2, 3, 3, 3, 1, 1, 5, 2, 5, 1, 7, 3, 3, 4, 6, 4, 7, 4, 1, 9, 5, 3, 2, 4, 7, 2, 9, 2
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OFFSET
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1,4
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LINKS
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EXAMPLE
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n=1: 2*prime(1)+prime(1+1)=2*2+3=7 is prime, so a(1)=1;
n=2: 2*prime(2)+prime(2+1)=2*3+5=11 is prime, so a(2)=1;
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n=4: 2*prime(4)+prime(4+1)=2*7+11=25 is not prime
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2*prime(4)+prime(4+3)=2*7+17=31 is prime, so a(4)=3.
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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++; p2 = Prime[n1 + n2]]; n2, {n1, 1, 200}]
mnm[n_]:=Module[{m=1, p=2Prime[n]}, While[!PrimeQ[p+Prime[n+m]], m++]; m]; Array[mnm, 110] (* Harvey P. Dale, Aug 05 2017 *)
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PROG
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(Haskell)
a114266 n = head [m | m <- [1..],
a010051 (2 * a000040 n + a000040 (n + m)) == 1]
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CROSSREFS
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Cf. A114227, A114230, A073703, A114235, A114262, A114228, A114231, A114233, A114236, A114263, A114265, A114267.
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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