A332848 - OEIS

%I #12 Mar 19 2023 12:16:47

%S 809,15331,51071,59183,59447,95747,125737,224069,442733,471677,521869,

%T 579757,651517,658873,659453,696989,890887,893449,1035707,1114193,

%U 1236517,1271807,1299041,1337593,1435201,1585513,1590383,1672271,1707073,1708363,1817131,1835003,1963309,1992527,2078371,2329597

%N Primes p such that (3*p+q)/2, (p+3*q)/2, (3*q+r)/2 and (q+3*r)/2 are all prime, where q and r are the next primes after p.

%C The first of two consecutive primes that are both in A329151.

%C The first case where a(n+1) is the next prime after a(n), i.e. a(n) and the next two primes are all in A329151, is a(176)=35103361.

%H Robert Israel, <a href="/A332848/b332848.txt">Table of n, a(n) for n = 1..2000</a>

%e a(3) = 51071 is in the sequence because p=51071, q=51109, r=51131 are consecutive primes such that (3*p+q)/2=102161, (p+3*q)/2=102199, (3*q+r)/2=102229, (q+3*r)/2=102251 are all prime.

%p q:= 3: r:= 5:

%p count:= 0: Res:= NULL:

%p while count < 100 do

%p   p:= q; q:= r; r:= nextprime(q);

%p   if isprime((3*p+q)/2) and isprime((p+3*q)/2) and isprime((3*q+r)/2)

%p   and isprime((q+3*r)/2) then

%p     count:= count+1; Res:= Res, p;

%p   fi

%p od:

%p Res;

%t Select[Partition[Prime[Range[175000]],3,1],AllTrue[{(3#[[1]]+#[[2]])/2,(#[[1]]+ 3#[[2]])/2,(3#[[2]]+#[[3]])/2,(#[[2]]+3#[[3]])/2},PrimeQ]&][[;;,1]] (* _Harvey P. Dale_, Mar 19 2023 *)

%Y Cf. A329151.

%K nonn

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Feb 26 2020