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 A183186 #22 May 05 2024 00:21:00
%S A183186 88,112,198,622,4228,10052,55862
%N A183186 Numbers k such that 10^(2k+1) - 4*10^k - 1 is prime.
%D A183186 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A183186 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp959">Palindromic Wing Primes (PWP's)</a>.
%H A183186 Makoto Kamada, <a href="https://stdkmd.net/nrr/9/99599.htm#prime">Prime numbers of the form 99...99599...99</a>.
%H A183186 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A183186 a(n) = (A077786(n) - 1)/2.
%t A183186 Do[If[PrimeQ[10^(2n + 1) - 4*10^n - 1], Print[n]], {n, 3000}]
%o A183186 (PARI) is(n)=ispseudoprime(10^(2*n+1)-4*10^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A183186 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A183186 nonn,base
%O A183186 1,1
%A A183186 _Ray Chandler_, Dec 28 2010