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A237837 Number of primes p < n such that the number of Sophie Germain primes among 1, ..., n-p is a cube.

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%I A237837 #10 Apr 06 2014 22:22:38
%S A237837 0,0,1,2,1,1,1,1,1,0,0,1,1,1,1,0,0,1,1,1,1,0,0,1,1,0,0,0,0,1,1,1,1,0,
%T A237837 0,0,0,1,1,0,0,1,1,1,1,0,0,1,1,0,0,0,0,1,2,2,2,3,3,5,5,5,5,5,5,6,6,7,
%U A237837 7,7,7,9,9,9,9,9,9,9,9,10
%N A237837 Number of primes p < n such that the number of Sophie Germain primes among 1, ..., n-p is a cube.
%C A237837 Conjecture: a(n) > 0 for all n > 53.
%H A237837 Zhi-Wei Sun, <a href="/A237837/b237837.txt">Table of n, a(n) for n = 1..10000</a>
%H A237837 Z.-W. Sun, <a href="http://arxiv.org/abs/1402.6641">Problems on combinatorial properties of primes</a>, arXiv:1402.6641, 2014
%e A237837 a(55) = 2 since 53 is prime and there is exactly 1^3 = 1 Sophie Germain prime not exceeding 55 - 53 = 2, and 2 is prime and there are exactly 2^3 = 8 Sophie Germain primes not exceeding 55 - 2 = 53 (namely, they are 2, 3, 5, 11, 23, 29, 41, 53).
%t A237837 sg[n_]:=Sum[If[PrimeQ[2*Prime[k]+1],1,0],{k,1,PrimePi[n]}]
%t A237837 CQ[n_]:=IntegerQ[n^(1/3)]
%t A237837 a[n_]:=Sum[If[CQ[sg[n-Prime[k]]],1,0],{k,1,PrimePi[n-1]}]
%t A237837 Table[a[n],{n,1,80}]
%Y A237837 Cf. A000040, A000578, A005384, A237815.
%K A237837 nonn
%O A237837 1,4
%A A237837 _Zhi-Wei Sun_, Feb 13 2014