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 A183183 #21 Jan 17 2019 13:44:08
%S A183183 1,2,8,19,20,212,280,887,1021,5515,8116,11852
%N A183183 Numbers n such that (7*10^(2n+1)+18*10^n-7)/9 is prime.
%C A183183 a(13) > 10^5. - _Robert Price_, Jan 19 2016
%D A183183 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A183183 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp797">Palindromic Wing Primes (PWP's)</a>
%H A183183 Makoto Kamada, <a href="https://stdkmd.net/nrr/7/77977.htm#prime">Prime numbers of the form 77...77977...77</a>
%H A183183 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A183183 a(n) = (A077796(n)-1)/2.
%t A183183 Do[If[PrimeQ[(7*10^(2n + 1) + 18*10^n - 7)/9], Print[n]], {n, 3000}]
%o A183183 (PARI) is(n)=ispseudoprime((7*10^(2*n+1)+18*10^n-7)/9) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A183183 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A183183 nonn,more,base
%O A183183 1,2
%A A183183 _Ray Chandler_, Dec 28 2010