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A079139 Numbers n such that (Product of first n twin prime pair averages [A014574] ) + 1 is prime. 1
1, 5, 45, 218, 506, 538, 1027 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(3) and a(4) certified prime with Primo.
LINKS
EXAMPLE
a(2) = 5 because the product of the first five terms of A014574 + 1, 4*6*12*18*30 + 1 = 155521, is prime.
MATHEMATICA
seq = {1}; prod = 4; k = 1; Do[If[AllTrue[6 n + {-1, 1}, PrimeQ], prod *= 6 n; k++; If[PrimeQ[prod + 1], AppendTo[seq, k]]], {n, 1, 5000}]; seq (* Amiram Eldar, Dec 14 2019 *)
PROG
(PARI) { atp(N)= local(t, c); t=1; c=0; forprime(p=2, N, if(isprime(p+2), t*=p+1; c++; if(isprime(t+1), print1(c, ", ")))) }
CROSSREFS
Cf. A014574.
Sequence in context: A201876 A351426 A027801 * A269911 A249638 A188349
KEYWORD
nonn,more
AUTHOR
Jason Earls, Dec 26 2002
EXTENSIONS
a(7) from Amiram Eldar, Dec 14 2019
STATUS
approved

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Last modified April 23 13:11 EDT 2024. Contains 371913 sequences. (Running on oeis4.)