|
Search: id:A111145
|
|
|
| A111145 |
|
Length of the Cunningham chain initiated by the n-th Sophie Germain prime. |
|
+0
1
|
|
| 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, 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, 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
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
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.
|
|
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 (noe(AT)sspectra.com), Jun 06 2006
|
|
CROSSREFS
|
Cf. A005384, A057331.
Sequence in context: A019901 A157121 A083241 this_sequence A021660 A064853 A112597
Adjacent sequences: A111142 A111143 A111144 this_sequence A111146 A111147 A111148
|
|
KEYWORD
|
nice,nonn
|
|
AUTHOR
|
Christopher M. Tomaszewski (cmt1288(AT)comcast.net), Oct 18 2005
|
|
EXTENSIONS
|
More terms from T. D. Noe (noe(AT)sspectra.com), Jun 06 2006
|
|
|
Search completed in 0.002 seconds
|
