|
Search: id:A123998
|
|
|
| A123998 |
|
Numbers n such that 2n+1 and 4n+1 are primes. |
|
+0
13
|
|
| 1, 3, 9, 15, 18, 39, 48, 69, 78, 99, 105, 114, 135, 153, 165, 168, 183, 189, 219, 249, 273, 288, 300, 303, 309, 330, 345, 363, 405, 414, 438, 468, 483, 498, 504, 534, 585, 618, 639, 648, 699, 714, 729, 765, 804, 813, 828, 879, 933, 1005, 1014, 1044, 1065, 1068
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
Note that if n == 1 mod 3 then 2n+1 is not prime (except n=1); and if n == 2 mod 3 then 4n+1 is not prime. Therefore n must be a multiple of 3, except for n=1. - Max Alekseyev, Nov 02 2006
|
|
MATHEMATICA
|
Select[Range[1100], And @@ PrimeQ /@ ({2, 4}*# + 1) &] (*Chandler*)
|
|
CROSSREFS
|
Cf. A005097, A005098, A124408-A124411, A071576.
Adjacent sequences: A123995 A123996 A123997 this_sequence A123999 A124000 A124001
Sequence in context: A071123 A071347 A093414 this_sequence A117105 A136410 A029506
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Artur Jasinski (grafix(AT)csl.pl), Oct 31 2006
|
|
EXTENSIONS
|
Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 20 2006
|
|
|
Search completed in 0.002 seconds
|
