A079139 Numbers n such that (Product of first n twin prime pair averages [A014574] ) + 1 is prime.
1, 5, 45, 218, 506, 538, 1027, 8153
Offset: 1
Examples
a(2) = 5 because the product of the first five terms of A014574 + 1, 4*6*12*18*30 + 1 = 155521, is prime.
Crossrefs
Cf. A014574.
Programs
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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 *) -
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, ", ")))) }
Extensions
a(7) from Amiram Eldar, Dec 14 2019
a(8) from Michael S. Branicky, Aug 05 2024
Comments