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A093701
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a(n) = smallest m>a(n-1) such that 1+m*n is prime, a(1) = 1.
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2
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1, 2, 4, 7, 8, 10, 16, 17, 18, 19, 30, 31, 34, 35, 36, 37, 38, 41, 58, 59, 62, 64, 72, 73, 76, 77, 80, 81, 84, 85, 88, 95, 96, 97, 102, 103, 106, 111, 114, 118, 122, 123, 124, 125, 130, 132, 134, 135, 138, 140, 142, 144, 150, 152, 156, 158, 164, 166, 174, 175
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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For n=3: we have a(2)=2, so we want the smallest number m > 2 such that n*m+1 = 3*m+1 is prime. m=3 fails but m=4 works, so a(3) = m = 4. - N. J. A. Sloane, Dec 13 2018
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MATHEMATICA
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nxt[{n_, a_}]:=Module[{m=a+1}, While[!PrimeQ[m(n+1)+1], m++]; {n+1, m}]; NestList[ nxt, {1, 1}, 60][[All, 2]] (* Harvey P. Dale, Dec 13 2018 *)
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CROSSREFS
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Note that A081942 is a related but distinct sequence.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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