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A173750
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a(n) = smallest positive m such that k*m+1 is prime for k=2..n.
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0
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1, 1, 2, 330, 714, 13530, 192660, 512820, 4601310, 863815050, 262428279750, 2169289182060, 2169289182060, 2169289182060, 4646092391146085880
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OFFSET
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1,3
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LINKS
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Table of n, a(n) for n=1..15.
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MATHEMATICA
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a[n_] := Block[{k = If[n < 4, 1, 6], s}, s = k; While[! AllTrue[k Range[2, n] + 1, PrimeQ], k += s]; k]; Array[a, 9] (* Giovanni Resta, Mar 30 2017 *)
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PROG
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(Magma) S:=[]; m:=1; for n in [1..11] do while not forall(t){ k: k in [2..n] | IsPrime(k*m+1) } do m+:=1; end while; Append(~S, m); end for; S; // Klaus Brockhaus, Nov 26 2010
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CROSSREFS
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Cf. A088250 (smallest number k such that r*k+1 is prime for all r = 1 to n).
Sequence in context: A012601 A012606 A012729 * A088250 A142355 A203608
Adjacent sequences: A173747 A173748 A173749 * A173751 A173752 A173753
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KEYWORD
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nonn,more
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AUTHOR
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Zak Seidov, Nov 26 2010
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EXTENSIONS
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a(12)-a(15) from Giovanni Resta, Mar 31 2017
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STATUS
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approved
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