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 A124477 #21 Sep 17 2020 06:41:13
%S A124477 0,1,5,341,5461,21845,89478485,96076792050570581,
%T A124477 25790417485112089060398421,6760803201217223474649083762005,
%U A124477 7089215977519551322153637654828504405
%N A124477 Numbers k such that 24k+7 is a Mersenne prime (A000668).
%C A124477 Note that 2^m - 1 can be expressed as 24*k+7 whenever m is an odd integer >= 3. - _Robert Israel_, Jul 08 2014
%H A124477 Michel Marcus, <a href="/A124477/b124477.txt">Table of n, a(n) for n = 1..18</a>
%F A124477 a(n) = (2^A000043(n+1)-8)/24. - _Jeppe Stig Nielsen_, Sep 17 2020
%p A124477 seq((numtheory:-mersenne([i+1])-7)/24, i=1..20); # _Robert Israel_, Jul 08 2014
%o A124477 (PARI) for(n=0, 1e20, k=0; if(ispseudoprime(24*n+7), while(2^k-1 < 24*n+7, k++); if(24*n+7==2^k-1, print1(n, ", ")))) \\ _Felix Fröhlich_, Jul 04 2014
%o A124477 (PARI) lista(nn) = {vmps = readvec("b000043.txt"); if (nn== 0, nn = #vmps); for (i=1, nn, mpi = 2^vmps[i]-8; if ((mpi % 24) == 0, print1(mpi/24, ", ")););} \\ _Michel Marcus_, Jul 05 2014
%Y A124477 Cf. A000043, A000668, A139480.
%K A124477 nonn
%O A124477 1,3
%A A124477 _Artur Jasinski_, Dec 17 2006
%E A124477 a(11) corrected by _Michel Marcus_, Jul 05 2014