%I #16 Mar 20 2018 19:02:32

%S 2,5,7,13,31,41,43,59,101,107,127,137,149,199,239,277,359,389,479,613,

%T 743,757,809,829,937,991,1031,1103,1439,1487,1499,1847,1877,2011,2083,

%U 2179,2609,2663,2711,2741,2749,2857,2909,3329,3559,3623,3643,3697,3823

%N p and A002808(p)/2 are both prime.

%C Primes p such that composite(p) is an even semiprime.

%H Robert Israel, <a href="/A177997/b177997.txt">Table of n, a(n) for n = 1..10000</a>

%e a(1)=2 because 2=prime and composite(2)/2=6/2=3=prime.

%p P,C:= selectremove(isprime, [$2..10000]):

%p select(t -> t <= nops(C) and C[t]::even and isprime(C[t]/2), P); # _Robert Israel_, Mar 20 2018

%o (PARI)

%o c=[]; for(n=2, 10000, if(!isprime(n), c=concat(c, n))); c; \\ The composites

%o s=[]; forprime(p=2, #c, if(c[p]%2==0 && isprime(c[p]\2), s=concat(s, p))); s \\ _Colin Barker_, Jun 28 2014

%Y Cf. A002808, A065858, A065897.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, May 17 2010, May 23 2010

%E Corrected by _D. S. McNeil_ and _R. J. Mathar_, May 23 2010