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 A088274 #67 Apr 03 2023 10:36:10
%S A088274 1,2,4,8,9,24,60,110,134,222,412,700,999,1383,5076,5543,6344,14600,
%T A088274 15093,21717,23636,30221,50711,221628,350071,371696,487291,995256,
%U A088274 1043372
%N A088274 Numbers k such that 10^k + 7 is prime.
%C A088274 No other terms less than 59500.
%C A088274 No other terms <= 100000. - _Robert Price_, Mar 03 2011
%C A088274 a(28) > 500000. - _Alfred Reich_, Jun 10 2021
%C A088274 a(29) > 1000000. - _Alfred Reich_, Nov 20 2021
%C A088274 a(30) > 1075000. - _Alfred Reich_, Jan 10 2022
%H A088274 G. L. Honaker, Jr. and Chris Caldwell, eds., <a href="https://t5k.org/curios/page.php/1000000007.html">Prime Curios!</a>
%H A088274 Makoto Kamada, <a href="https://stdkmd.net/nrr/1/10007.htm#prime">Prime numbers of the form 100...007</a>.
%H A088274 Alfred Reich, <a href="https://www.alfredreichlg.de/10w7/prp/ProofFile.200001-1000000.txt">ProofFile</a>.
%H A088274 Alfred Reich, <a href="https://www.alfredreichlg.de/10w7/prp/ProofFile.1000001-1075000.txt">ProofFile2</a>.
%H A088274 Sabin Tabirca and Kieran Reynolds, <a href="http://multimedia.ucc.ie/Staff/ST/articles/SNJ03_Tabirca1.ps">Lacunary Prime Numbers</a>.
%F A088274 a(n) = A102007(n) + 1.
%e A088274 8 is a term since 10^8 + 7 = 100000007 is a prime.
%t A088274 Do[ If[ PrimeQ[ 10^n + 7], Print[n]], {n, 0, 10000}] (* _Robert G. Wilson v_, Dec 16 2004 *)
%o A088274 (PARI) is(n)=isprime(10^n + 7) \\ _Charles R Greathouse IV_, Apr 29 2015
%Y A088274 Cf. A088275, A049054, A102007, A159031.
%K A088274 nonn,more
%O A088274 1,2
%A A088274 _Amarnath Murthy_, Sep 28 2003
%E A088274 a(7)-a(14) from _Ray Chandler_, Oct 09 2003
%E A088274 a(15)-a(19) from _Robert G. Wilson v_, Jan 18 2005
%E A088274 Corrected and extended by _Jason Earls_, Nov 27 2007 and Dec 07 2007. (14600 was missing and 23636 and 50711 are new. These are presently only probable primes, found with WinPFGW.)
%E A088274 Missing term 30221 added by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E A088274 a(24)-a(27) from _Alfred Reich_, Jun 10 2021
%E A088274 a(28) from _Alfred Reich_, Nov 20 2021
%E A088274 a(29) from _Alfred Reich_, Jan 10 2022