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A231326 Primes p such that p - 2*k is also prime, where p is k-th prime. 2


%S 17,19,23,37,47,67,71,73,83,89,97,113,131,137,139,149,151,157,167,179,

%T 181,197,199,223,233,263,307,331,353,379,397,419,421,439,443,457,461,

%U 463,503,557,587,613,631,641,643,659,661,677,701,719,743,761,773,839,863

%N Primes p such that p - 2*k is also prime, where p is k-th prime.

%H K. D. Bajpai, <a href="/A231326/b231326.txt">Table of n, a(n) for n = 1..5200</a>

%e a(2)= 19 which is 8th prime. prime(8)-2*8= 19-16= 3 which is also prime.

%e a(6)= 67 which is 19th prime. prime(19)-2*19= 67-38= 29 which is also prime.

%p KD := proc() local a,b; a:= ithprime(n); b := a-2*n; if isprime(b) then RETURN (a); fi;end: seq(KD(),n=1..500);

%t TK = Select[Table[{Prime[n], Prime[n] - 2*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[TK][[1]]

%Y Cf. A061068 (primes: prime(m) plus its subscript).

%Y Cf. A064402 (numbers n: prime(n)+n is prime).

%Y Cf. A227420 (primes: p - pi(p) is also prime).

%Y Cf. A231232 (primes: prime(k)+2*k is also prime).

%K nonn

%O 1,1

%A _K. D. Bajpai_, Nov 07 2013

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Last modified July 26 22:10 EDT 2021. Contains 346300 sequences. (Running on oeis4.)