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 A130327 Least prime p such that 3*p*2^n-1 and 3*p*2^n+1 are twin primes. 4

%I

%S 2,2,5,3,5,2,11,3,19,17,5,113,59,317,331,307,241,2,829,23,149,127,11,

%T 3023,1091,787,971,1523,2741,727,1051,227,211,727,89,1163,71,367,1031,

%U 577,89,1213,1151,3,1021,283,2699,4933,59,647,709

%N Least prime p such that 3*p*2^n-1 and 3*p*2^n+1 are twin primes.

%H Pierre CAMI, <a href="/A130327/b130327.txt">Table of n, a(n) for n = 0..200</a>

%e 3*2*2^0-1=5, 3*2*2^0+1=7: 5 and 7 are twin primes so for n=0 p=2.

%e 3*2*2^1-1=11, 3*2*2^1+1=13: 11 and 13 are twin primes so for n=1 p=2.

%o (PARI) a(n) = my(p=2); while (!(isprime(q=3*p*2^n-1) && isprime(q+2)), p=nextprime(p+1)); p; \\ _Michel Marcus_, Sep 23 2019

%Y Cf. A130325, A130326.

%K nonn

%O 0,1

%A _Pierre CAMI_, May 24 2007

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Last modified July 15 23:32 EDT 2020. Contains 335774 sequences. (Running on oeis4.)