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A071127 Number of times there is a prime p < n such that 2n+p is prime. 3


%S 0,0,0,1,1,1,2,2,1,1,1,2,3,2,3,2,3,4,2,4,4,2,2,5,4,2,5,5,2,6,3,3,6,4,

%T 4,5,3,5,6,4,3,6,5,3,8,3,6,8,5,5,6,4,4,7,6,2,6,4,3,11,5,4,9,5,5,9,7,6,

%U 9,6,3,10,6,4,11,7,6,10,5,9,11,5,6,12,8,5,10,6,6,13,7,6,11,8,8,11,7,8,11

%N Number of times there is a prime p < n such that 2n+p is prime.

%H T. D. Noe, <a href="/A071127/b071127.txt">Table of n, a(n) for n=1..10000</a>

%e a(7)=2 because 14+3 and 14+5 are primes.

%t For[lst={}; n=1, n<=100, n++, cnt=0; k=1; While[Prime[k]<n, If[PrimeQ[2n+Prime[k]], cnt++ ]; k++ ]; AppendTo[lst, cnt]]; lst

%Y Cf. A071137.

%K easy,nonn

%O 1,7

%A _T. D. Noe_, May 28 2002

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Last modified September 25 02:25 EDT 2021. Contains 347651 sequences. (Running on oeis4.)