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 A077789 #31 Mar 26 2020 11:12:49
%S A077789 7,67,623,5867,44471,78331,83171
%N A077789 Numbers k such that (10^k - 1)/9 + 6*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
%C A077789 Prime versus probable prime status and proofs are given in the author's table.
%C A077789 a(8) > 10^5. - _Robert Price_, Apr 30 2017
%D A077789 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A077789 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp171">Palindromic Wing Primes (PWP's)</a>
%H A077789 Makoto Kamada, <a href="https://stdkmd.net/nrr/1/11711.htm#prime">Prime numbers of the form 11...11711...11</a>
%H A077789 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A077789 a(n) = 2*A107127(n) + 1.
%e A077789 7 is a term because (10^7 - 1)/9 + 6*10^3 = 1117111.
%t A077789 Do[ If[ PrimeQ[(10^n + 54*10^Floor[n/2] - 1)/9], Print[n]], {n, 3, 6000, 2}] (* _Robert G. Wilson v_, Dec 16 2005 *)
%Y A077789 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A077789 more,nonn,base
%O A077789 1,1
%A A077789 _Patrick De Geest_, Nov 16 2002
%E A077789 a(5)-a(7) from _Robert Price_, Apr 30 2017
%E A077789 Name corrected by _Jon E. Schoenfield_, Oct 31 2018