login
Numbers m such that 2*prime(m)+prime(m+1) is prime.
0

%I #7 Oct 13 2024 17:42:20

%S 1,2,3,6,7,8,10,17,22,27,29,30,35,45,48,49,50,52,53,57,61,68,70,80,81,

%T 85,94,104,106,117,120,125,126,127,131,132,136,137,138,143,146,156,

%U 157,166,177,191,198,206,220,223,224,225,233,236,244,248,254,259,261,262

%N Numbers m such that 2*prime(m)+prime(m+1) is prime.

%F a(n) = pi(A173971(n))=A000720(A173971(n)).

%o (PARI) {my(a=2);for(n=1,1000,my(b=nextprime(a+1));isprime(2*a+b)&print1(n,", ");a=b)}

%Y Cf. A000040 The prime numbers.

%Y A173971 Primes p such that 2*p+NextPrime are prime numbers.

%Y A000720 pi(n), the number of primes <= n.

%K easy,nonn

%O 1,2

%A _Zak Seidov_, Oct 10 2010