cp's OEIS Frontend

A307818 Numbers k such that A240718(k) = 0.

%I A307818 #14 Jul 22 2021 02:07:35
%S A307818 1,2,3,4,5,6,9,12,15,19,49,61,63,64,110,151,154,166,173,244,278,427,
%T A307818 454,481,496,572,575,637,677,680,681,691,704,712,766,884,928,964,1039,
%U A307818 1094,1100,1219,1256,1265,1309,1321,1729,1909,1924,2309,2443,2686,2989,3001,3004,3713,4798,4801,5134,5311,5719,5821,6443,6574,6781,7099,7339,8251,9454,10684,11416,11713,11728,21766,27122,31637
%N A307818 Numbers k such that A240718(k) = 0.
%C A307818 k is in the sequence if there are no primes p < sqrt(2*k-2) such that 2*k-p is prime.
%C A307818 There are no other terms < 10^7.
%C A307818 Conjecture: 31637 is the last term.
%e A307818 a(7)=9 is in the sequence because the primes < sqrt(2*9-2)=4 are 2 and 3, and neither 2*9-2=16 nor 2*9-3=15 is prime.
%p A307818 P:= NULL: Res:= 1:  nextp:= 2:
%p A307818 for n from 2 to 10^6 do
%p A307818   while nextp^2 < 2*n-2 do
%p A307818    P:= P, nextp;
%p A307818    nextp:= nextprime(nextp);
%p A307818   od;
%p A307818   if andmap(t -> not isprime(2*n-t), [P]) then
%p A307818    Res:= Res, n
%p A307818   fi;
%p A307818 od:
%p A307818 Res;
%Y A307818 Cf. A240718.
%K A307818 nonn
%O A307818 1,2
%A A307818 _Robert Israel_, Apr 30 2019