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 A068648 #19 Jul 08 2020 11:57:20
%S A068648 11,181,188888881,188888888888881,
%T A068648 18888888888888888888888888888888888888881,
%U A068648 188888888888888888888888888888888888888888888888888888888888888888888888888888888888888888881
%N A068648 Primes in which a string of 8's is sandwiched between two 1's.
%C A068648 The next term -- a(7) -- has 129 digits. - _Harvey P. Dale_, Jul 08 2020
%H A068648 Patrick De Geest, <a href="http://www.worldofnumbers.com/deplat.htm#pdp181">PDP Reference Table - 181</a>.
%H A068648 Makoto Kamada, <a href="https://stdkmd.net/nrr/1/18881.htm#prime">Prime numbers of the form 188...881</a>.
%H A068648 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%e A068648 11 is also a member in which a string of 0 8's is there between two one's.
%p A068648 a := 1:b := 8:i := 1:for n from 0 to 500 do c := a+10*(10^n-1)/9*b+10^(n+1)*a; if(isprime(c)) then d[i] := c; i := i+1; end if; end do:q := seq(d[j],j=1..i-1);
%t A068648 Select[Table[10FromDigits[PadRight[{1},n,8]]+1,{n,100}],PrimeQ] (* _Harvey P. Dale_, Jul 08 2020 *)
%Y A068648 Cf. A068645-A068651, A056249, A082702.
%K A068648 base,nonn
%O A068648 1,1
%A A068648 _Amarnath Murthy_, Feb 28 2002
%E A068648 More terms from _Sascha Kurz_, Mar 19 2002
%E A068648 Edited by _Ray Chandler_, Nov 04 2014