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 A077790 #37 Oct 30 2023 18:05:23
%S A077790 3,7,15,23,27,35,59,63,67,155,1867,3111,23517,235415
%N A077790 Numbers k such that (10^k - 1)/3 + 4*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
%C A077790 Prime versus probable prime status and proofs are given in the author's table.
%C A077790 a(14) > 200000. - _Robert Price_, Dec 29 2016
%D A077790 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A077790 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp373">Palindromic Wing Primes (PWP's)</a>
%H A077790 Makoto Kamada, <a href="https://stdkmd.net/nrr/3/33733.htm#prime">Prime numbers of the form 33...33733...33</a>
%H A077790 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A077790 a(n) = 2*A183176(n) + 1.
%e A077790 23 is a term because (10^23 - 1)/3 + 4*10^11 = 33333333333733333333333.
%t A077790 Do[ If[ PrimeQ[(10^n + 12*10^Floor[n/2] - 1)/3], Print[n]], {n, 3, 23600, 2}] (* _Robert G. Wilson v_, Dec 16 2005 *)
%Y A077790 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A077790 more,nonn,base
%O A077790 1,1
%A A077790 _Patrick De Geest_, Nov 16 2002
%E A077790 Name corrected by _Jon E. Schoenfield_, Oct 31 2018
%E A077790 a(14) from _Robert Price_, Oct 30 2023