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A109927 First primes p connected to two primes either by 2p+1 or 2p-1 upward [downward (p-1)/2 or (p+1)/2]. 3
3, 5, 11, 23, 37, 83, 157, 179, 359, 661, 719, 877, 997, 1019, 1237, 1439, 1657, 2039, 2063, 2137, 2459, 2557, 2819, 2903, 2963, 3023, 3061, 3623, 3779, 3803, 3863, 4177, 4261, 4357, 4621, 4919, 5399, 5581, 5639, 6037, 6121, 6217, 6361, 6899, 6983, 7079 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

These primes may be part of Cunningham chains longer than three terms. It seems the two operators are never mixed, except for 3, 5 and 7: -for 3, we have: 2 through <2p-1> -> 3 through <2p+1> -> 7 -for 5: 3 <2p-1> -> 5 <2p+1> -> 11 -for 7: 3 <2p+1> -> 7 <2p-1> -> 13

LINKS

Table of n, a(n) for n=1..46.

Chris Caldwell's Prime Glossary, Cunningham chains.

EXAMPLE

a(3)=11 is here because 5->11->23 through <2p+1>;

a(4)=23 because 11->23->47 through <2p+1>;

a(5)=37 because 19->37->73 through <2p-1>.

PROG

Terms computed by Gilles Sadowski.

CROSSREFS

Cf. A005382, A005383, A005384, A005385, A059455, A068497.

Sequence in context: A049436 A117010 A056874 * A146276 A155753 A133914

Adjacent sequences:  A109924 A109925 A109926 * A109928 A109929 A109930

KEYWORD

easy,nonn

AUTHOR

Alexandre Wajnberg, Aug 31 2005

STATUS

approved

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Last modified April 21 08:49 EDT 2014. Contains 240824 sequences.