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A124492 a(n) = least k such that 2*i*k - 1 is prime for 1 <= i <= n. 7
2, 2, 2, 3, 3, 77385, 1447110, 1447110, 203937090, 107290072890, 4724240531010, 123618251967210, 1272603355923900, 9089306184994125090 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
a[n_] := Block[{k = If[n < 6, 1, 5], s}, s = k; While[! AllTrue[k 2 Range[n] - 1, PrimeQ], k += s]; k]; Array[a, 8] (* Giovanni Resta, Apr 01 2017 *)
CROSSREFS
Sequence in context: A131704 A327746 A348626 * A338629 A057646 A238892
KEYWORD
nonn,more
AUTHOR
Artur Jasinski, Nov 04 2006
EXTENSIONS
Corrected and extended by Don Reble, Nov 05 2006
a(12)-a(14) from Giovanni Resta, Apr 01 2017
STATUS
approved

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Last modified April 22 02:54 EDT 2024. Contains 371887 sequences. (Running on oeis4.)