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 A006553 M1575 #35 Sep 08 2022 08:44:35 %S A006553 1,2,6,10,18,40,46,86,118,170,1172,1698,1810,2268,4338,18362,72662, %T A006553 88392,94110,161538,168660,292340,401208,560750,1035092 %N A006553 Numbers k such that k*3^k - 1 is prime. %D A006553 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006553 Steven Harvey, <a href="http://harvey563.tripod.com/GeneralizedWoodallPrimes.txt">Generalized Woodall Search</a> %t A006553 Select[Range[10000], PrimeQ[# 3^# - 1] &] (* _Vincenzo Librandi_, Dec 02 2015 *) %o A006553 (Magma) [n: n in [0..1420] | IsPrime(n*3^n-1)]; // _Vincenzo Librandi_, Dec 02 2015 %o A006553 (PARI) is(n)=ispseudoprime(n*3^n-1) \\ _Charles R Greathouse IV_, Feb 20 2017 %K A006553 hard,nonn %O A006553 1,2 %A A006553 _N. J. A. Sloane_ %E A006553 More terms from _Jud McCranie_ %E A006553 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008 %E A006553 a(24)-a(25) from Harvey link by _Ray Chandler_, Apr 10 2016