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A120394
a(1) is the least k such that p(1) = (k*7)^2 + k*7 - 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
3, 1, 6, 4, 157, 31, 10, 306, 751, 222, 1296, 4939
OFFSET
1,1
COMMENTS
The p(n) sequence starts 461, 212981, 1632993906881, ...
EXAMPLE
a(1) = 3 as (3*7)^2 + 3*7 - 1 = 461 = p(1) is prime.
MATHEMATICA
f[0] = {0, 7}; 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
KEYWORD
nonn
AUTHOR
Pierre CAMI, Jul 01 2006
EXTENSIONS
a(9)-a(12) from Amiram Eldar, Aug 28 2021
STATUS
approved