OFFSET
1,1
COMMENTS
LINKS
T. D. Noe, Table of n, a(n) for n = 1..10000
EXAMPLE
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.
MATHEMATICA
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, Jun 06 2006
ccl[n_]:=Length[NestWhileList[2#+1&, n, PrimeQ[2#+1]&]]; ccl/@Select[ Prime[ Range[1000]], PrimeQ[2#+1]&] (* Harvey P. Dale, Sep 29 2018 *)
CROSSREFS
KEYWORD
nice,nonn
AUTHOR
Christopher M. Tomaszewski (cmt1288(AT)comcast.net), Oct 18 2005
EXTENSIONS
More terms from T. D. Noe, Jun 06 2006
STATUS
approved