This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A231506 #6 Nov 09 2013 19:04:04 %S A231506 7,13,19,53,71,101,107,139,173,199,223,229,281,293,397,463,557,569, %T A231506 673,787,809,839,953,1013,1283,1451,1559,1657,1861,1871,1877,1949, %U A231506 1987,1997,2213,2311,2347,2357,2377,2503,2543,2551,2593,2633,2837,2851,2939,2999,3041 %N A231506 Primes p such that p + 3*k and p - 3*k, both are primes, where p is k-th prime. %H A231506 K. D. Bajpai, <a href="/A231506/b231506.txt">Table of n, a(n) for n = 1..5200</a> %e A231506 a(7)= 107 which is 28th prime. prime(28)-3*28= 107-84= 23: prime(28)+3*28= 107+84= 191: 23 and 191 both are primes. %e A231506 a(9)= 173 which is 40th prime. prime(40)-3*40= 173-120= 53: prime(40)+3*40= 173+120= 293: 53 and 293 both are primes. %p A231506 KD := proc() local a,b,d; a:= ithprime(n); b:= abs(a-3*n);d:=(a+3*n); if isprime(b) and isprime(d) then RETURN (a); fi; end: seq(KD(), n=1..500); %Y A231506 Cf. A061068 (primes: prime(m) plus its subscript). %Y A231506 Cf. A064402 (numbers n: prime(n)+n is prime). %Y A231506 Cf. A231232 (primes p : p+2*k is also primes). %Y A231506 Cf. A231383 (primes p : p+3*k is also primes). %K A231506 nonn %O A231506 1,1 %A A231506 _K. D. Bajpai_, Nov 09 2013