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 A099005 #36 May 31 2023 15:54:55
%S A099005 1,2,3,4,6,7,8,12,23,59,75,144,204,268,760,1216,1430,1506,1509,2804,
%T A099005 2924,3201,3305,5753,9268,11279,19677,23414,28627,31362,42299,49119,
%U A099005 63747,81767,111443,263720,264791
%N A099005 Numbers k such that 4*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
%C A099005 Also numbers k such that (14*10^k - 11)/3 is a prime number.
%C A099005 a(38) > 3*10^5. - _Robert Price_, Mar 30 2015
%H A099005 Makoto Kamada, <a href="https://stdkmd.net/nrr/4/46663.htm#prime">Prime numbers of the form 466...663</a>.
%H A099005 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A099005 a(n) = A101730(n) + 1.
%e A099005 For n = 1, 2, 3, 4, 6, 7, 8 are members since 43, 463, 4663, 46663, 4666663, 46666663 and 466666663 are primes.
%t A099005 Do[ If[ PrimeQ[(14*10^n - 11)/3], Print[n]], {n, 0, 10000}] (* _Robert G. Wilson v_, Dec 17 2004 *)
%Y A099005 Cf. A101730.
%K A099005 more,nonn
%O A099005 1,2
%A A099005 Julien Peter Benney (jpbenney(AT)ftml.net), Nov 07 2004
%E A099005 a(15) - a(21) from _Robert G. Wilson v_, Dec 22 2004
%E A099005 a(22) - a(25) from _Robert G. Wilson v_, Jan 17 2005
%E A099005 a(26)-a(27) from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E A099005 a(28)-a(29) from Kamada data by _Robert Price_, Dec 08 2010
%E A099005 a(30)-a(32) from Erik Branger, May 01 2013, submitted by _Ray Chandler_, Aug 16 2013
%E A099005 a(33)-a(34) from Kamada data by _Robert Price_, Mar 30 2015
%E A099005 a(35)-a(37) from _Robert Price_, May 31 2023