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 A183175 #27 Aug 03 2024 18:58:06
%S A183175 1,2,17,79,118,162,177,185,240,824,1820,2354,134811
%N A183175 Numbers k such that (10^(2k+1) + 6*10^k - 1)/3 is prime.
%C A183175 a(13) > 10^5. - _Robert Price_, Apr 03 2016
%D A183175 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A183175 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp353">Palindromic Wing Primes (PWP's)</a>.
%H A183175 Makoto Kamada, <a href="https://stdkmd.net/nrr/3/33533.htm#prime">Prime numbers of the form 33...33533...33</a>.
%H A183175 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A183175 a(n) = (A077784(n) - 1)/2.
%t A183175 Do[If[PrimeQ[(10^(2n + 1) + 6*10^n - 1)/3], Print[n]], {n, 3000}]
%o A183175 (PARI) is(n)=ispseudoprime((10^(2*n+1)+6*10^n-1)/3) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A183175 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A183175 nonn,base
%O A183175 1,2
%A A183175 _Ray Chandler_, Dec 28 2010
%E A183175 a(13) from _Robert Price_, Aug 03 2024