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 A103851 Numbers k such that 2*prime(k)+1, 2*prime(k+1)+1 and 2*prime(k+2)-1 are also consecutive primes. 2
 2, 119, 372, 814, 4350, 9797, 16625, 16729, 40224, 45191, 48121, 63137, 71520, 83264, 89744, 94166, 103551, 109538, 111283, 113690, 117620, 232363, 265101, 268661, 269466, 302024, 316847, 329793, 333947, 334725, 340910, 352997, 380914, 381169, 384459, 385927 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 2*3+1 = 5, 2*5+1 = 7, 2*7 - 1 = 13; 3, 5 and 7 are consecutive primes as are 5, 7 and 13, so a(1) = 2 as 3 = prime(2). MATHEMATICA s={}; n=1; p1=2; p2=3; Do[p3 = NextPrime[p2]; If[PrimeQ[2*p1+1] && (np = NextPrime[2*p1+1]) == 2*p2+1 && NextPrime[np] == 2*p3-1, AppendTo[s, n]]; p1=p2; p2=p3; n++, {10^5}]; s (* Amiram Eldar, Jul 23 2021 *) CROSSREFS Cf. A103852. Sequence in context: A013511 A013507 A013476 * A024030 A221231 A243512 Adjacent sequences: A103848 A103849 A103850 * A103852 A103853 A103854 KEYWORD nonn AUTHOR Pierre CAMI, Feb 18 2005 EXTENSIONS Corrected by T. D. Noe, Nov 02 2006 a(21) and a(30) inserted and a(36) added by Amiram Eldar, Jul 23 2021 STATUS approved

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Last modified March 4 08:20 EST 2024. Contains 370522 sequences. (Running on oeis4.)