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 A266694 #35 Sep 08 2022 08:46:15 %S A266694 1,2,3,14,19,21,27,33,46,70,80,441,540,567,625,1057,1119,1213,1542, %T A266694 4263,4419,4507,5186,7345,8626,8853,11256,12885,14688,15236,17697, %U A266694 26770,57801,71665 %N A266694 Numbers n such that 2*n*3^n + 1 is prime. %C A266694 Primes: 2, 3, 19, 1213, 4507, ... %C A266694 No further terms < 10^5. - _Ray Chandler_, Apr 13 2016 %e A266694 1 is in this sequence because 2*1*3^1 + 1 = 7 is prime. %t A266694 Select[Range[1600], PrimeQ[2 # 3^# + 1] &] (* _Vincenzo Librandi_, Jan 03 2016 *) %o A266694 (Magma) [n: n in [1..2000]| IsPrime(2*n*3^n+1)]; // _Vincenzo Librandi_, Jan 03 2016 %o A266694 (PARI) is(n)=ispseudoprime(2*n*3^n+1) \\ _Charles R Greathouse IV_, Feb 08 2016 %Y A266694 Cf. A006552. %K A266694 nonn,more %O A266694 1,2 %A A266694 _Juri-Stepan Gerasimov_, Jan 02 2016 %E A266694 a(24) and a(26) inserted by _Charles R Greathouse IV_, Feb 08 2016 %E A266694 a(28)-a(30) from _Charles R Greathouse IV_, Feb 08 2016 %E A266694 a(31)-a(32) from _Ray Chandler_, Apr 05 2016 %E A266694 a(33) from _Ray Chandler_, Apr 08 2016 %E A266694 a(34) from _Ray Chandler_, Apr 09 2016