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 A293907 #28 Mar 29 2023 12:48:42
%S A293907 6,12,14,24,28,34,46,48,52,56,68,72,84,92,96,112,117,123,126,136,144,
%T A293907 168,186,192,204,208,224,228,249,252,266,272,288,328,336,356,372,384,
%U A293907 392,408,416,448,464,488,498,504,516
%N A293907 Numbers n for which 10^n mod n = 2^k for some positive integer k.
%C A293907 Odd numbers in this sequence: 117, 123, 249, 747, 4043, 5031, 11573, 12129, 14481, 29489, 34719, 35549, 84123, 124631, 173329, 217391, 266799, 458523, 472173, 490561, 551759, 658499, 675431, 721773, 800397, 1375569, 1917843, 2300079, 3194787, 3394893, 4236747, 5031039, 5043957, 5169333, ....
%H A293907 Charles R Greathouse IV, <a href="/A293907/b293907.txt">Table of n, a(n) for n = 1..10000</a>
%e A293907 For n = 6, 10^6 mod 6 = 4 = 2^2;
%e A293907 For n = 14, 10^14 mod 14 = 2 = 2^1;
%e A293907 For n = 84, 10^84 mod 84 = 64 = 2^6;
%e A293907 For n = 272, 10^272 mod 272 = 256 = 2^8.
%t A293907 pm2Q[n_]:=Module[{c=PowerMod[10,n,n]},c>1&&IntegerQ[Log2[c]]]; Select[ Range[600],pm2Q] (* _Harvey P. Dale_, Mar 29 2023 *)
%o A293907 (PARI) is(n)=my(k=lift(Mod(10,n)^n)); k>1 && k>>valuation(k,2)==1 \\ _Charles R Greathouse IV_, Oct 19 2017
%Y A293907 Cf. A056969 (10^n modulo n).
%K A293907 nonn
%O A293907 1,1
%A A293907 _Björn Ch. Buchli_, Oct 19 2017
%E A293907 More terms from _Michel Marcus_, Oct 19 2017