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 A063679 #34 Nov 29 2022 02:41:21
%S A063679 4,12,18,26,106,164,246,956,2554,3350,6496,8706,9008,15398,15490,
%T A063679 20408,39240,41060,41842,58358,60346,82214,134972,194014,344204,
%U A063679 587712,778070
%N A063679 Numbers k such that (3^k - 7)/2 is prime.
%C A063679 x = 3^k is a solution to sigma(x - 7) = sigma(x) - 7 when (3^k - 7)/2 is prime.
%C A063679 a(28) > 10^6
%e A063679 (3^4 - 7)/2 = 37 is prime, so 4 is in the sequence.
%p A063679 with(numtheory):i := 0:x := 1:while i < 1000 do i := i+1:x := 3*x: if isprime((x-7)/2) then print(i):fi:od:
%t A063679 Do[ If[ PrimeQ[ (3^n - 7)/2 ], Print[n] ], {n, 2, 5500} ]
%t A063679 Select[Range[2, 10000], PrimeQ[((3^# - 7)/2)] &] (* _Vincenzo Librandi_, Sep 30 2012 *)
%o A063679 (PARI) is(n)=ispseudoprime((3^n-7)/2) \\ _Charles R Greathouse IV_, May 22 2017
%Y A063679 Cf. A000203, A063680, A015913-A015917, A054905, A116970.
%K A063679 nonn,more
%O A063679 1,1
%A A063679 _Jud McCranie_, Jul 28 2001
%E A063679 More terms from _Robert G. Wilson v_, Aug 02 2001
%E A063679 0, 1 removed and a(11)-a(13) added from _Vincenzo Librandi_, Sep 30 2012
%E A063679 a(14)-a(17) from _Seth A. Troisi_, Oct 17 2022
%E A063679 a(17) corrected, a(18)-a(25) from _Seth A. Troisi_, Oct 29 2022
%E A063679 a(26)-a(27) from _Seth A. Troisi_, Nov 28 2022