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 A228121 #21 Mar 30 2020 19:28:00 %S A228121 2,3,5,7,9,11,15,17,19,21,25,29,31,35,37,39,45,47,51,57,59,61,65,67, %T A228121 77,79,81,85,87,89,91,95,99,105,107,117,119,121,129,131,135,141,145, %U A228121 149,151,155,157,161,165,169,171,175,187,189,191,197,199,201,207,215,217,219,221,227,229 %N A228121 Numbers n such that 3n - 4 is prime. %C A228121 Primes in a(n): 2, 3, 5, 7, 11, 17, 19, 29, 31, 37, 47, 59, 61, 67, 79, 89, 107, 131, 149, 151, 157, 191, 197, 199, 227, 229, 241, 271, 277, 281,... %H A228121 Harvey P. Dale, <a href="/A228121/b228121.txt">Table of n, a(n) for n = 1..1000</a> %F A228121 a(n) = A024893(n) + 2. - _Michael B. Porter_, Aug 11 2013 %e A228121 For n = 15, 3*15 - 4 = 41 is prime. %t A228121 Select[Range[300],PrimeQ[3#-4]&] (* _Harvey P. Dale_, Mar 30 2020 *) %o A228121 (PARI) is(n)=isprime(3*n-4) \\ _Charles R Greathouse IV_, Mar 17 2014 %Y A228121 Cf. A008585, A153183, A228358. %K A228121 nonn,less,easy %O A228121 1,1 %A A228121 _Irina Gerasimova_, Aug 11 2013