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A079140 Numbers n such that (Product of first n twin prime pair averages [A014574]) - 1 is prime. 0
1, 2, 7, 11, 16, 32, 402, 1107, 1829, 2584, 3124, 6936 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Some of the larger entries may only correspond to probable primes.

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

a(2) = 2 because the product of the first two terms of A014574 - 1, 4 * 6-1 = 23, 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) {atm(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: A190518 A190750 A049635 * A176897 A166005 A243009

Adjacent sequences:  A079137 A079138 A079139 * A079141 A079142 A079143

KEYWORD

nonn,more

AUTHOR

Jason Earls, Dec 26 2002

EXTENSIONS

a(8)-a(12) from Amiram Eldar, Dec 14 2019

STATUS

approved

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Last modified May 14 19:53 EDT 2021. Contains 343903 sequences. (Running on oeis4.)