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 A183174 #31 Apr 30 2024 05:51:54
%S A183174 1,3,7,61,90,92,269,298,321,371,776,1567,2384,2566,3088,5866,8051,
%T A183174 9498,12635,24512,32521,43982
%N A183174 Numbers k such that (10^(2k+1) - 6*10^k - 1)/3 is prime.
%C A183174 a(23) > 10^5. - _Robert Price_, Jan 29 2016
%D A183174 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H A183174 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp313">Palindromic Wing Primes (PWP's)</a>.
%H A183174 Makoto Kamada, <a href="https://stdkmd.net/nrr/3/33133.htm#prime">Prime numbers of the form 33...33133...33</a>.
%H A183174 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A183174 a(n) = (A077775(n) - 1)/2.
%t A183174 Do[If[PrimeQ[(10^(2n + 1) - 6*10^n - 1)/3], Print[n]], {n, 3000}]
%o A183174 (PARI) for(n=1,1e3,if(ispseudoprime((10^(2*n+1)-6*10^n-1)/3),print1(n", "))) \\ _Charles R Greathouse IV_, Jul 15 2011
%Y A183174 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K A183174 nonn,base
%O A183174 1,2
%A A183174 _Ray Chandler_, Dec 28 2010
%E A183174 a(21)-a(22) from _Robert Price_, Jan 29 2016