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 A124490 Numbers n such that 2n-1, 4n-1, 6n-1, 8n-1, 10n-1, 12n-1 and 14n-1 are primes. 1

%I #13 Oct 11 2019 11:07:08

%S 1447110,2623005,4095000,4339335,6975780,9080190,12382755,19455975,

%T 20322960,30020760,32261985,54202995,62014155,63196350,66383520,

%U 71369340,94571295,121012185,124225920,162780660,177109380,196068180,223888665,303047745,310143960

%N Numbers n such that 2n-1, 4n-1, 6n-1, 8n-1, 10n-1, 12n-1 and 14n-1 are primes.

%t Select[3*5*7*Range[2000000], And @@ PrimeQ /@ ({2, 4, 6, 8, 10, 12, 14}*# - 1) &] (* _Ray Chandler_, Nov 21 2006 *)

%t pr7Q[n_]:=AllTrue[2*Range[7]n-1,PrimeQ]; Select[105*Range[3*10^6],pr7Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, May 17 2018 *)

%Y Cf. A124485-A124492.

%K nonn

%O 1,1

%A _Artur Jasinski_, Nov 04 2006

%E Extended by _Ray Chandler_, Nov 21 2006

%E More terms from _Harvey P. Dale_, May 17 2018

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