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 A254248 #29 Feb 04 2021 07:02:05
%S A254248 0,1,1,18,262,3393,39541,421863,4457974,46853770,482301801,4931928485
%N A254248 Number of terms in A006285 (de Polignac numbers) less than 10^n.
%C A254248 a(n) < 10^n*exp(-(n*log(10))^c) for some c.
%H A254248 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_219.htm">Puzzle 219. Polignac numbers</a>, The Prime Puzzles and Problems Connection.
%t A254248 dePolignacQ[n_] := OddQ[n] && Module[{m = 2}, While[n > m + 1 && ! PrimeQ[n - m], m *= 2]; n <= m + 1]; seq[max_] := Module[{p = 10, c = 1, s = {0}}, Do[If[dePolignacQ[k], c++]; If[k == p, p *= 10; AppendTo[s, c]], {k, 5, 10^max}]; s]; seq[6] (* _Amiram Eldar_, Feb 04 2021 *)
%Y A254248 Cf. A006285, A255816, A255971, A256164, A256238.
%K A254248 nonn,more
%O A254248 0,4
%A A254248 _Arkadiusz Wesolowski_, Mar 16 2015
%E A254248 a(9) from _Arkadiusz Wesolowski_, Feb 09 2016
%E A254248 a(10)-a(11) from _Amiram Eldar_, Feb 04 2021