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 A077776 #33 Mar 26 2020 11:52:39
%S A077776 3,11,27,87,339,363,3159,36155,45305,314727
%N A077776 Numbers k such that (10^k - 1) - 8*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
%C A077776 Prime versus probable prime status and proofs are given in the author's table.
%D A077776 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A077776 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp919">Palindromic Wing Primes (PWP's)</a>
%H A077776 Makoto Kamada, <a href="https://stdkmd.net/nrr/9/99199.htm#prime">Prime numbers of the form 99...99199...99</a>
%H A077776 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A077776 a(n) = 2*A183184(n) + 1.
%e A077776 27 is a term because (10^27 - 1) - 8*10^13 = 999999999999919999999999999.
%t A077776 Do[ If[ PrimeQ[10^n - 8*10^Floor[n/2] - 1], Print[n]], {n, 3, 1000, 2}] (* _Robert G. Wilson v_, Dec 16 2005 *)
%Y A077776 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A077776 more,nonn,base
%O A077776 1,1
%A A077776 _Patrick De Geest_, Nov 16 2002
%E A077776 One more term from PWP table added by _Patrick De Geest_, Nov 05 2014
%E A077776 Name corrected by _Jon E. Schoenfield_, Oct 31 2018