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 A178421 Lower primes p1 in a twin pair such that sum of p1 and p2 yields average a1 of twin prime pairs and product of 2*a1 is another average of twin prime pairs. 4

%I

%S 211049,248639,253679,410339,507359,605639,1121189,1138829,1262099,

%T 2162579,2172869,2277659,4070219,6305459,7671509,11659409,12577109,

%U 14203769,14862119,17472839,18728639,18798359,20520569,21140699

%N Lower primes p1 in a twin pair such that sum of p1 and p2 yields average a1 of twin prime pairs and product of 2*a1 is another average of twin prime pairs.

%C 211049 is a term since 211049 and 211051 are twin primes; 211049 + 211051 = 422100 is an average of twin primes, and 2*422100 = 844200 is another average of twin primes.

%H Amiram Eldar, <a href="/A178421/b178421.txt">Table of n, a(n) for n = 1..10000</a>

%t lst={};Do[p1=Prime[n];p2=Prime[n+1];a1=p1+p2;a2=2*a1;If[p2-p1==2&&PrimeQ[a1-1]&&PrimeQ[a1+1]&&PrimeQ[a2-1]&&PrimeQ[a2+1],AppendTo[lst,p1]],{n,10!}];lst

%t atpQ[{a_,b_}]:=Module[{m=a+b},b-a==2&&AllTrue[m+{1,-1},PrimeQ] && AllTrue[ 2m+{1,-1},PrimeQ]]; Select[Partition[Prime[Range[134*10^4]],2,1],atpQ][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 28 2019 *)

%Y Cf. A001097, A014574, A069142, A099349.

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 27 2010

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Last modified September 18 10:31 EDT 2020. Contains 337166 sequences. (Running on oeis4.)