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 A228830 #15 Mar 11 2019 16:03:22 %S A228830 2,3,5,23,37,43,59,89,103,127,149,151,163,197,199,277,347,379,409,443, %T A228830 449,487,617,619,631,641,643,823,829,853,859,887,929,953,997,1069, %U A228830 1151,1181,1303,1321,1381,1493,1499,1543,1583,1613,1637,1747,1867,1889,2027,2053 %N A228830 Primes p(n) such that 2*p(n) + p(2n) is prime. %H A228830 Charles R Greathouse IV, <a href="/A228830/b228830.txt">Table of n, a(n) for n = 1..10000</a> %e A228830 3 is in the sequence, being the second prime, as we verify that 2 * prime(2) + prime(2 * 2) = 2 * 3 + 7 = 13, which is also prime. %e A228830 5 is in the sequence, being the third prime, as we see that 2 * prime(3) + prime(2 * 3) = 2 * 5 + 13 = 23, which is also prime. %e A228830 7 is not in the sequence, since it gives 2 * prime(4) + prime(2 * 4) = 2 * 7 + 19 = 33 = 3 * 11, which is not prime. %t A228830 Prime[Select[Range[300], PrimeQ[2Prime[#] + Prime[2#]] &]] (* _Alonso del Arte_, Sep 08 2013 *) %t A228830 Select[Prime[Range[350]],PrimeQ[2#+Prime[2PrimePi[#]]]&] (* _Harvey P. Dale_, Mar 11 2019 *) %o A228830 (PARI) v=List(); n=q=0;forprime(p=2,1e4,if(n++%2,next); q=nextprime(q+1);if(isprime(2*q+p), listput(v,q))); Vec(v) \\ _Charles R Greathouse IV_, Sep 05 2013 %Y A228830 Cf. A228727. %K A228830 nonn %O A228830 1,1 %A A228830 _Irina Gerasimova_, Sep 04 2013 %E A228830 Terms corrected by _Charles R Greathouse IV_, Sep 05 2013