A124849
Numbers k such that 7k + 3 and 3k + 7 are primes.
Original entry on oeis.org
0, 2, 4, 8, 10, 22, 32, 34, 40, 44, 50, 52, 58, 68, 74, 88, 92, 110, 122, 134, 142, 160, 164, 178, 188, 208, 212, 242, 250, 260, 268, 272, 304, 320, 334, 344, 352, 370, 374, 382, 388, 398, 424, 428, 440, 458, 464, 472, 484, 494, 508, 520, 524, 538, 550, 554, 572
Offset: 1
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[n: n in [0..1000] | IsPrime(7*n+3) and IsPrime(3*n+7)] // Vincenzo Librandi, Mar 26 2010
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Select[Range[0,600],AllTrue[{7#+3,3#+7},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 27 2018 *)
A124850
Primes p=n/2 such that 7n+3 and 3n+7 are primes.
Original entry on oeis.org
2, 5, 11, 17, 29, 37, 61, 67, 71, 89, 167, 191, 199, 229, 269, 277, 311, 331, 337, 347, 379, 389, 419, 431, 509, 541, 577, 587, 617, 631, 691, 709, 757, 797, 809, 821, 929, 941, 977, 991, 1069, 1091, 1117, 1129, 1217, 1277, 1279, 1289, 1291, 1367, 1439
Offset: 1
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Select[Prime[Range[250]],AllTrue[{14#+3,6#+7},PrimeQ]&] (* Harvey P. Dale, Mar 10 2022 *)
A181766
Numbers k such that 3*k + 7 is not prime.
Original entry on oeis.org
1, 3, 5, 6, 7, 9, 11, 13, 14, 15, 16, 17, 19, 21, 23, 25, 26, 27, 28, 29, 31, 33, 35, 36, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 51, 53, 54, 55, 56, 57, 59, 60, 61, 63, 65, 66, 67, 69, 70, 71, 73, 75, 76, 77, 79, 80, 81, 82, 83, 84, 85, 86, 87, 89, 91, 93, 94, 95, 96, 97, 98
Offset: 1
Distribution of the even terms in the following triangular array:
*;
*, 6;
*, *,14;
*, *,*,*;
*,16,*,*,38;
*,*,28,*,*,54;
*,*, *,*,*, *,*;
*,26,*,*,60,*,*,94;
*,*,42,*,*,80,*,*,118;
*,*,*, *,*,*, *,*, *, *;
*,36,*,*,82,*,*,128,*,*,174;
*,*,56,*,*,106,*,*,156,*,*,206; etc.
where * marks the non-integer values of (4*h*k + 2*k + 2*h - 6)/3 with h >= k >= 1. - _Vincenzo Librandi_, Jan 15 2013
Showing 1-3 of 3 results.
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