%I
%S 1,2,6,7,14,15,17,18,19,20,21,26,27,28,29,31,33,35,36,38,39,42,44,45,
%T 48,49,53,55,56,57,59,61,64,65,66,69,70,71,74,76,77,78,79,80,82,84,87,
%U 88,89,90,91,92,93,96,98,99,100,102,103,104,105,107,109,112,113,115,117
%N Numbers k such that 2*prime(k)1 and 2*prime(k)+1 are both prime or both composite.
%e 1 is a term because 2*prime(1)  1 = 3 (prime) and 2*prime(1) + 1 = 5 (prime);
%e 2 is a term because 2*prime(2)  1 = 5 (prime) and 2*prime(2) + 1 = 7 (prime),
%e 7 is a term because 2*prime(7)  1 = 33 (composite) and 2*prime(7) + 1 = 35 (composite).
%p for n from 1 to 200 do p := ithprime(n) ; if isprime(2*p1) = isprime(2*p+1) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Apr 20 2010
%Y Cf. A100484.
%K nonn
%O 1,2
%A _JuriStepan Gerasimov_, Apr 14 2010
%E Corrected (6 inserted, 74 inserted) by _R. J. Mathar_, Apr 20 2010
