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 A084198 Primes p such that there exists exactly one prime q

%I

%S 5,7,19,43,67,97,163,181,211,283,331,349,523,547,601,691,787,853,907,

%T 937,1021,1051,1123,1171,1429,1531,1549,1723,1777,1867,2011,2029,2053,

%U 2083,2113,2251,2281,2347,2371,2467,2521,2707,2731,2749,2803,2971,3067

%N Primes p such that there exists exactly one prime q<p with q+1 dividing p+1.

%C A084196(A049084(a(n)))=1.

%H Reinhard Zumkeller, <a href="/A084198/b084198.txt">Table of n, a(n) for n = 1..1000</a>

%t pdQ[n_]:=Module[{prs=Prime[Range[500]],p1},p1=Select[prs,#<n&]+1;Count[ p1,_?(Divisible[n+1,#]&)]==1]; Select[Prime[Range[500]],pdQ] (* _Harvey P. Dale_, Dec 24 2013 *)

%o a084198 n = a084198_list !! (n-1)

%o a084198_list = map a000040 \$ filter ((== 1) . a084196) [1..]

%o -- _Reinhard Zumkeller_, Jan 06 2014

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, May 18 2003

%E Corrected by _T. D. Noe_, Oct 25 2006

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Last modified August 18 08:57 EDT 2019. Contains 326077 sequences. (Running on oeis4.)