cp's OEIS Frontend

A342993 Numbers of the form prime(i-1)+prime(i+1) that are the average of a twin prime pair.

%I A342993 #15 Apr 05 2021 03:58:10
%S A342993 72,150,180,270,1032,1062,1452,1608,2028,2082,2130,2592,2790,3120,
%T A342993 3258,3300,3360,3930,4020,4272,4650,4722,4788,4932,5442,5880,6702,
%U A342993 7128,7332,7878,8388,8430,8862,9240,9342,9678,10008,10140,10272,10890,11490,11940,12072,12162,12918,13002,13218,13932
%N A342993 Numbers of the form prime(i-1)+prime(i+1) that are the average of a twin prime pair.
%H A342993 Robert Israel, <a href="/A342993/b342993.txt">Table of n, a(n) for n = 1..10000</a>
%e A342993 a(3) = 180 is a term because 180 = 83 + 97 = prime(23)+prime(25) and (180-1 = 179, 180+1 = 181) is a twin prime pair.
%p A342993 count:= 0: R:= NULL:
%p A342993 for i from 1 while count < 100 do
%p A342993   x:= ithprime(i)+ithprime(i+2);
%p A342993   if isprime(x-1) and isprime(x+1) then R:= R, x; fi
%p A342993 od:
%p A342993 R;
%o A342993 (PARI) lista(nn) = {for (n=2, nn, my(x=prime(n)+prime(n+2)); if (isprime(x-1) && isprime(x+1), print1(n, ", ")););} \\ _Michel Marcus_, Apr 02 2021
%Y A342993 Intersection of A048448 and A014574.
%Y A342993 Cf. A000040.
%K A342993 nonn
%O A342993 1,1
%A A342993 _J. M. Bergot_ and _Robert Israel_, Apr 01 2021