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 A099422 #35 Apr 16 2024 02:41:28
%S A099422 1,2,3,5,8,9,15,51,71,77,224,296,315,2090,2906,3395,3882,5114,6056,
%T A099422 7254,7995,18173,18971,35006,69674,175428,253313
%N A099422 Numbers k such that 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
%C A099422 Also numbers k >= 1 such that (8*10^k - 53)/9 is prime.
%C A099422 a(26) > 10^5. - _Robert Price_, Oct 31 2014
%H A099422 Makoto Kamada, <a href="https://stdkmd.net/nrr/8/88883.htm#prime">Prime numbers of the form 88...883</a>.
%H A099422 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%F A099422 a(n) = A056694(n) + 1.
%t A099422 Do[ If[ PrimeQ[ 8(10^n - 1)/9 - 5], Print[n]], {n, 1, 5000}]
%o A099422 (Magma) [n: n in [1..500] | IsPrime((8*10^n-53) div 9)]; // _Vincenzo Librandi_, Nov 01 2014
%Y A099422 Cf. A002275, A056664, A056694, A093166.
%K A099422 nonn
%O A099422 1,2
%A A099422 _Robert G. Wilson v_, Oct 14 2004
%E A099422 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
%E A099422 a(22)-a(25) from _Robert Price_, Oct 31 2014
%E A099422 a(1)=0 removed by _Georg Fischer_, Jan 03 2021
%E A099422 a(26)-a(27) from Kamada data by _Tyler Busby_, Apr 16 2024