A358047 - OEIS

%I #14 Nov 14 2022 09:54:31

%S 2,3,5,7,17,13,11,19,23,37,29,31,41,67,47,43,53,61,59,73,83,97,89,79,

%T 71,109,113,127,167,157,107,103,101,151,131,139,179,163,137,193,191,

%U 181,239,199,149,211,197,223,173,241,227,229,233,277,257,283,263,271,269,349,293

%N a(1) = 2; afterwards a(n) is the least new prime such that 2*a(n-1) + a(n) is a prime.

%C Sequence is non-monotone. Are all primes in the sequence?

%t s = {n = 2}; Do [p = 3; While [MemberQ[s, p] || !PrimeQ[2*n + p], p = NextPrime[p]]; AppendTo[s, n = p]; p = NextPrime[p], {100}]; s

%o (PARI) lista(nn) = my(va = vector(nn), last=2); va[1] = last; for (n=2, nn, my(p=2); while(!isprime(2*last+p) || #select(x->(x==p), va), p = nextprime(p+1)); va[n] = p; last = p;); va; \\ _Michel Marcus_, Nov 14 2022

%K nonn

%O 1,1

%A _Zak Seidov_, Oct 27 2022