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%I #16 Mar 11 2014 12:48:14
%S 3,7,13,19,31,41,47,53,61,71,79,89,101,107,113,139,151,173,193,199,
%T 223,229,239,251,271,281,293,349,373,397,433,457,463,521,541,557,569,
%U 593,601,613,619,641,647,673,683,743,787,809,839,911,941,953,971,1013,1049
%N Primes p such that abs(p - 3*k) is also prime, where p is the k-th prime.
%H K. D. Bajpai, <a href="/A231432/b231432.txt">Table of n, a(n) for n = 1..6400</a>
%e The first prime, 2, is not a term since |2-3*1| = 1.
%e The second prime, 3, is a term, since |3-2*3| = 3 is a prime.
%e a(11) = 79 which is the 22nd prime, prime(22)-3*22 = 79-66 = 13 which is also prime.
%e a(15) = 113 which is the 30th prime, prime(30)-3*30 = 113-90 = 23 which is also prime.
%p KD := proc() local a, b; a:= ithprime(n); b:= abs(a-3*n); if isprime(b) then RETURN (a); fi; end: seq(KD(), n=1..500);
%t KD = Select[Table[{Prime[n], Prime[n] - 3*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[KD][[1]]
%o (PARI) k=0;forprime(p=2,1e3,if(isprime(abs(p-k++*3)), print1(p", "))) \\ _Charles R Greathouse IV_, Mar 11 2014
%Y Cf. A061068 (primes: prime(m) plus its subscript).
%Y Cf. A064402 (numbers n: prime(n)+n is prime).
%Y Cf. A231232 (primes p : p+2*k is also prime).
%Y Cf. A231383 (primes p : p+3*k is also prime).
%K nonn,easy
%O 1,1
%A _K. D. Bajpai_, Nov 09 2013
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