A275219 - OEIS

%I #10 Jul 22 2016 22:10:26

%S 3,5,10,13,13,19,18,37,33,35,51,34,32,61,78,58,59,78,50,67,90,91,137,

%T 133,66,62,64,71,212,241,133,106,168,184,122,181,162,165,192,139,216,

%U 216,110,109,264,463,337,127,123,210,184,263,355,282,271,200,193

%N Number of primes between prime (n)*prime (n + 1) and prime (n + 1) prime (n + 2).

%H Clark Kimberling, <a href="/A275219/b275219.txt">Table of n, a(n) for n = 1..1000</a>

%e The primes between 15 and 35 are 17,19,23,29,31, so that a(2) = 5.

%t z = 200; t = Table[Prime[n] Prime[n + 1], {n, 1, 2*z}]  (* A006094 *)

%t Table[PrimePi[t[[n + 1]]] - PrimePi[t[[n]]], {n, 1, z}] (* A275219 *)

%o (PARI) a(n) = primepi(prime(n+1)*prime(n+2)) - primepi(prime(n)*prime(n+1)) \\ _Felix Fröhlich_, Jul 22 2016

%Y Cf. A000040, A006094.

%K nonn,easy

%O 1,1

%A _Clark Kimberling_, Jul 20 2016