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 A005539 M2337 #33 Sep 08 2022 08:44:33
%S A005539 0,1,3,4,7,9,12,18,22,102,112,157,162,289,619,763,1389,1783,1882,3294,
%T A005539 3567,13297,14932,18954,19612,23598,33882,66874,70546,86568,187626,
%U A005539 190738
%N A005539 Numbers k such that 10*3^k + 1 is prime.
%C A005539 a(33) > 2*10^5. - _Robert Price_, Mar 16 2014
%C A005539 All terms are verified primes (i.e., not merely probable primes). - _Robert Price_, Mar 16 2014
%D A005539 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A005539 H. C. Williams and C. R. Zarnke, <a href="https://doi.org/10.1090/S0025-5718-1972-0314747-X">Some prime numbers of the forms 2*3^n+1 and 2*3^n-1</a>, Math. Comp., 26 (1972), 995-998.
%t A005539 Do[ If[ PrimeQ[ 10*3^n + 1], Print[n]], {n, 0, 6810}]
%o A005539 (Magma) [n: n in [0..3567] | IsPrime(10*3^n + 1) ]; // _Vincenzo Librandi_, Sep 26 2012
%o A005539 (PARI) is(n)=ispseudoprime(10*3^n+1) \\ _Charles R Greathouse IV_, Feb 20 2017
%K A005539 hard,nonn
%O A005539 1,3
%A A005539 _N. J. A. Sloane_
%E A005539 More terms from _Robert G. Wilson v_, Sep 07 2000
%E A005539 a(1)=0 added and typo in Mathematica program fixed by _Vincenzo Librandi_, Sep 26 2012
%E A005539 a(22)-a(32) from _Robert Price_, Mar 16 2014