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A124494 Numbers k for which 2*k-1, 4*k-1, 8*k-1 and 16*k-1 are primes. 7
3, 45, 90, 180, 255, 615, 705, 1350, 1770, 3225, 5295, 5775, 5955, 6060, 8580, 9855, 9945, 11175, 13095, 13740, 15195, 21825, 26820, 26925, 27615, 28920, 30075, 30705, 31710, 33375, 35700, 37350, 37665, 41250, 43770, 49185, 50700, 52185, 53640 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
Select[3*Range[20000], And @@ PrimeQ /@ ({2, 4, 8, 16}*# - 1) &] (* Ray Chandler, Nov 22 2006 *)
CROSSREFS
Sequence in context: A360966 A079038 A101790 * A075320 A071968 A170921
KEYWORD
nonn
AUTHOR
Artur Jasinski, Nov 04 2006
EXTENSIONS
Extended by Ray Chandler, Nov 22 2006
STATUS
approved

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Last modified April 23 03:30 EDT 2024. Contains 371906 sequences. (Running on oeis4.)