The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 Table of n, a(n) for n=1..7. 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 Adjacent sequences: A079136 A079137 A079138 * A079140 A079141 A079142 KEYWORD nonn,more AUTHOR Jason Earls, Dec 26 2002 EXTENSIONS a(7) from Amiram Eldar, Dec 14 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

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