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 A057472 #46 Sep 08 2022 08:45:02 %S A057472 1,2,3,4,5,12,16,26,27,36,40,45,49,52,53,75,140,150,167,245,250,755, %T A057472 785,825,970,1235,1289,1477,1739,1872,1976,1993,2175,4218,7656,10898, %U A057472 13410,13625,15706,33003,44288,45556,48855,60522,62795,98898,118429,153714 %N A057472 Numbers k such that 2*6^k - 1 is prime. %C A057472 a(49) > 2*10^5. - _Robert Price_, Jan 06 2016 [Since a(39) was missing before, this a(49) should actually be a(50). - _Jianing Song_, Sep 22 2018] %C A057472 Numbers k such that A164559(k+1) is prime. %t A057472 Select[Range[1000], PrimeQ[2*6^# - 1] &] (* _Giovanni Resta_, May 19 2016 *) %o A057472 (PARI) is(n)=ispseudoprime(2*6^n-1) \\ _Charles R Greathouse IV_, Feb 17 2017 %o A057472 (Magma) [n: n in [0..2000] |IsPrime(2*6^n - 1)]; // _Vincenzo Librandi_, Sep 23 2018 %Y A057472 Cf. A164559. %K A057472 nonn %O A057472 1,2 %A A057472 _Robert G. Wilson v_, Sep 10 2000 %E A057472 More terms from _Pierre CAMI_, Jun 16 2006 %E A057472 Edited by _Michel Marcus_, Jan 06 2012 %E A057472 a(41)-a(48) from _Robert Price_, Jan 06 2016 %E A057472 Missing a(39) from _Pierre CAMI_, May 19 2016