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 A124485 Numbers n such that 2n-1 and 4n-1 are primes. 17
 2, 3, 6, 12, 15, 21, 27, 42, 45, 57, 66, 87, 90, 96, 117, 120, 126, 141, 147, 180, 210, 216, 222, 246, 255, 297, 321, 327, 330, 342, 360, 372, 381, 405, 456, 477, 507, 510, 516, 525, 552, 612, 615, 645, 705, 720, 726, 741, 750, 756, 780, 792, 801, 867, 906, 945 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Muniru A Asiru, Table of n, a(n) for n = 1..5000 FORMULA a(n) = (A005384(n+1) + 1)/2. - Hilko Koning, Jul 19 2018 MAPLE select(k->isprime(2*k-1) and isprime(4*k-1), [\$1..1000]); # Muniru A Asiru, Jul 19 2018 MATHEMATICA Select[Range[1000], And @@ PrimeQ /@ ({2, 4}*# - 1) &] (* Ray Chandler, Nov 21 2006 *) PROG (GAP) Filtered([1..1000], p->IsPrime(2*p-1) and IsPrime(4*p-1)); # Muniru A Asiru, Jul 19 2018 CROSSREFS Cf. A005384 (Sophie Germain primes). Cf. A124486, A124487, A124488, A124489, A124490, A124491, A124492. Sequence in context: A217647 A070926 A226023 * A200175 A286906 A125867 Adjacent sequences:  A124482 A124483 A124484 * A124486 A124487 A124488 KEYWORD nonn AUTHOR Artur Jasinski, Nov 04 2006 EXTENSIONS Extended by Ray Chandler, Nov 21 2006 STATUS approved

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Last modified December 5 09:47 EST 2020. Contains 338945 sequences. (Running on oeis4.)