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A144722 a(n) is the smallest positive integer m such that b * (Product_{k=1..n} a(k)) + 1 is prime, with b = 3. 11
2, 3, 4, 6, 8, 21, 23, 26, 30, 36, 37, 39, 42, 54, 57, 73, 83, 86, 88, 91, 93, 98, 99, 112, 120, 137, 140, 142, 148, 161, 162, 169, 171, 174, 179, 237, 247, 294, 312, 335, 340, 382, 474, 475, 484, 498, 500, 539, 589, 598, 653, 654, 660, 704, 720, 732, 789, 804 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
3*1+1=4 is not prime (omitted).
a(1)=2 because 3*2+1=7 is prime.
a(2)=3 because 3*2*3+1=19 is prime.
MATHEMATICA
k = 3; a = {}; Do[If[PrimeQ[k*n + 1], k = k*n; AppendTo[a, n]], {n, 1, 3000}]; a
CROSSREFS
Sequence in context: A274456 A333681 A084074 * A105808 A124058 A274423
KEYWORD
nonn
AUTHOR
Artur Jasinski, Sep 19 2008
EXTENSIONS
Definition corrected by Georg Fischer, Jun 18 2021
STATUS
approved

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Last modified May 22 09:57 EDT 2024. Contains 372745 sequences. (Running on oeis4.)