A104294 - OEIS

%I #13 Mar 29 2015 18:08:19

%S 3,5,7,13,17,23,29,37,47,53,67,73,79,89,103,113,127,139,151,157,173,

%T 181,197,227,233,239,251,257,269,311,317,347,349,379,383,401,421,433,

%U 449,463,467,503,509,523,541,577,613,619,631

%N a(n) = prime((prime(n)+1)/2).

%C n=1 is a degenerate case because prime(1)=2, (prime(n)+1)/2 = 3/2 and there is no prime(3/2).

%F a(n) = A104293(n+1).

%F a(n) = A104295(n) + A104293(n).

%e a(5)=13 because prime((prime(5)+1)/2) = prime((11+1)/2) = prime(6) = 13;

%e a(7)=23 because prime((prime(7)+1)/2) = prime((17+1)/2) = prime(9) = 23.

%t Table[Prime[(Prime[n]+1)/2], {n, 2, 50}]

%o (PARI) vector(100,n,prime((prime(n+1)+1)/2)) \\ _Derek Orr_, Mar 29 2015

%Y Cf. A104293 (prime((prime(n)-1)/2)), A104295.

%K easy,nonn

%O 2,1

%A _Zak Seidov_, Feb 28 2005