Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #33 Jan 06 2017 07:54:14
%S 0,0,1,1,2,1,3,2,2,2,3,3,4,2,4,2,4,4,3,3,4,3,3,5,6,3,6,3,2,6,5,5,6,2,
%T 6,6,6,5,8,4,6,8,7,4,12,4,5,7,4,6,8,5,6,8,8,7,10,6,5,12,4,5,10,3,8,9,
%U 7,5,10,7,7,11,8,5,14,4,8,11,7,8,10,5,5,13,12,6,14,7,6,14,10,8,14
%N a(n) = number of primes of the form 4k + 3 such that 2n - 4k - 3 is prime.
%C Conjecture: a(n) > 0 for n >= 3.
%e a(5) = 2 because 2*5 - 4*0 - 3 = 7 is prime where 4*0 + 3 = 3 is prime of the form 4k+3 and 2*5 - 4*1 - 3 = 3 is prime where 4*1 + 3 = 7 is prime of the form 4k+3.
%Y Cf. A002145, A280134.
%K nonn
%O 1,5
%A _Juri-Stepan Gerasimov_, Dec 31 2016