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 A120396 a(1) is the least k such that p(1) = (k*17)^2 + k*17 - 1 is prime, then a(n+1) is the least k such that (k*p(n))^2 + k*p(n) - 1 = p(n+1) is prime. 3
 4, 4, 1, 46, 51, 197, 216, 225, 366, 1862, 3806, 116 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The p(n) sequence starts 4691, 352106459, 123978958821625139, ... LINKS Table of n, a(n) for n=1..12. EXAMPLE a(1) = 4 as (4*17)^2 + 4*17 - 1 = 4691 = p(1) is prime. MATHEMATICA f[0] = {0, 17}; f[n_] := f[n] = Module[{k = 1, p = f[n - 1][[2]]}, While[! PrimeQ[(k*p)^2 + k*p - 1], k++]; {k, (k*p)^2 + k*p - 1}]; Table[f[n][[1]], {n, 1, 10}] (* Amiram Eldar, Aug 28 2021 *) CROSSREFS Cf. A120392, A120393, A120394, A120395. Sequence in context: A136214 A067328 A111845 * A141024 A173210 A328922 Adjacent sequences: A120393 A120394 A120395 * A120397 A120398 A120399 KEYWORD nonn AUTHOR Pierre CAMI, Jul 01 2006 EXTENSIONS a(9)-a(12) from Amiram Eldar, Aug 28 2021 STATUS approved

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Last modified April 18 11:52 EDT 2024. Contains 371779 sequences. (Running on oeis4.)