A338771 - OEIS

%I #10 Nov 08 2020 23:04:11

%S 7,41,59,61,89,167,193,251,257,283,367,401,479,523,599,601,641,743,

%T 761,811,983,997,1087,1109,1117,1201,1277,1361,1429,1483,1619,1741,

%U 1789,1861,1889,1901,1931,2237,2297,2417,2609,2843,2897,2939,2971,3023,3121,3167,3373,3413,3457,3533,3719,3767

%N Primes p such that A338770(p) is prime.

%H Robert Israel, <a href="/A338771/b338771.txt">Table of n, a(n) for n = 1..3790</a>

%e a(3)=59 is in the sequence because 59 is prime and A338770(59) = 103 is prime.

%p filter:= proc(p) local q,v,t;

%p      t:= 0; q:= 1;

%p      do

%p        q:= nextprime(q);

%p        if 2*q > p then return isprime(t) fi;

%p        v:= p-2*q;

%p        if isprime(v) then t:= t+v fi;

%p      od

%p end proc:

%p select(filter, [seq(ithprime(i),i=1..2000)]);

%o (PARI) f(n) = my(s=0); forprime(p=0, n\2, if (isprime(q=n-2*p), s+=q)); s; \\ A338770

%o isok(p) = isprime(p) && isprime(f(p)); \\ _Michel Marcus_, Nov 08 2020

%Y Cf. A338770.

%K nonn

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Nov 08 2020