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 A183180 #33 Oct 12 2023 17:00:55
%S A183180 0,1,7,13,58,129,253,1657,2244,2437,7924,9903,11899,18157,18957,23665,
%T A183180 105609
%N A183180 Numbers k such that (7*10^(2k+1) - 18*10^k - 7)/9 is prime.
%C A183180 a(17) > 10^5. - _Robert Price_, Jun 23 2017
%C A183180 0 could be considered part of this sequence since the formula evaluates to 5 which is a degenerate form of the near-repdigit palindrome 777...77577...777 with 0 occurrences of the digit 7. - _Robert Price_, Jun 23 2017
%D A183180 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A183180 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp757">Palindromic Wing Primes (PWP's)</a>
%H A183180 Makoto Kamada, <a href="https://stdkmd.net/nrr/7/77577.htm#prime">Prime numbers of the form 77...77577...77</a>
%H A183180 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A183180 a(n) = (A077785(n) - 1)/2.
%t A183180 Do[If[PrimeQ[(7*10^(2n + 1) - 18*10^n - 7)/9], Print[n]], {n, 3000}]
%o A183180 (PARI) is(n)=ispseudoprime((7*10^(2*n+1)-18*10^n-7)/9) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A183180 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A183180 nonn,base
%O A183180 1,3
%A A183180 _Ray Chandler_, Dec 28 2010
%E A183180 a(16) from _Robert Price_, Jun 23 2017
%E A183180 a(17) from _Robert Price_, Oct 12 2023