Search: id:A111145
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%I A111145
%S A111145 5,2,4,3,2,2,3,2,2,6,2,2,2,5,2,2,2,2,2,2,4,2,2,2,2,4,2,2,2,2,2,3,2,2,2,
%T A111145 2,2,2,3,3,2,2,2,4,2,4,2,3,3,2,3,2,2,2,2,3,3,3,3,2,2,2,2,2,2,2,2,2,2,2,
%U A111145 2,3,2,2,2,4,2,2,3,2,2,2,2,2,2,2,2,2,2,3,3,4,2,2,2,2,2,3,2,2,3,2,2,2,2
%N A111145 Length of the Cunningham chain initiated by the n-th Sophie Germain prime.
%C A111145 If a(n) is a high-water mark of this sequence, then A057331(a(n)) is 
               the first term of the first Cunningham sequence of length a(n). For 
               example, a(10)=6 is a high-water mark of this sequence and A057331(a(10))=89 
               is the first term of the first Cunningham sequence of length 6.
%H A111145 T. D. Noe, <a href="b111145.txt">Table of n, a(n) for n=1..10000</a>
%e A111145 a(10)=6 because 89, the 10th Sophie Germain prime, is the first term 
               of the Cunningham chain 89, 179, 359, 719, 1439, 2879, which consists 
               of 6 terms.
%t A111145 lst=Select[Prime[Range[1000]], PrimeQ[2#+1]&]; Table[p=lst[[i]]; k=1; 
               While[p=2p+1; PrimeQ[p], k++ ]; k, {i,Length[lst]}] - T. D. Noe (noe(AT)sspectra.com), 
               Jun 06 2006
%Y A111145 Cf. A005384, A057331.
%Y A111145 Sequence in context: A019901 A157121 A083241 this_sequence A021660 A064853 
               A112597
%Y A111145 Adjacent sequences: A111142 A111143 A111144 this_sequence A111146 A111147 
               A111148
%K A111145 nice,nonn
%O A111145 1,1
%A A111145 Christopher M. Tomaszewski (cmt1288(AT)comcast.net), Oct 18 2005
%E A111145 More terms from T. D. Noe (noe(AT)sspectra.com), Jun 06 2006

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