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 A121031 #13 Jun 14 2024 18:55:09
%S A121031 11,110,1100,1111,1122,1133,1144,1155,1166,1177,1188,1199,2112,2211,
%T A121031 3113,3311,4114,4411,5115,5511,6116,6611,7117,7711,8118,8811,9119,
%U A121031 9911,11000,11011,11022,11033,11044,11055,11066,11077,11088,11099,11110
%N A121031 Multiples of 11 containing an 11 in their decimal representation.
%H A121031 Harvey P. Dale, <a href="/A121031/b121031.txt">Table of n, a(n) for n = 1..1000</a>
%H A121031 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%F A121031 a(n) ~ 11n. - _Charles R Greathouse IV_, Feb 12 2017
%t A121031 Select[11*Range[1100],MemberQ[Partition[IntegerDigits[#],2,1],{1,1}]&] (* _Harvey P. Dale_, Feb 16 2014 *)
%t A121031 Select[11Range[1100],SequenceCount[IntegerDigits[#],{1,1}]>0&] (* _Harvey P. Dale_, Jun 14 2024 *)
%o A121031 (PARI) is(n)=if(n%11, return(0)); while(n>10, if(n%100==11, return(1)); n\=10); 0 \\ _Charles R Greathouse IV_, Feb 12 2017
%Y A121031 Cf. A121041, A008593, A011531, A121022, A121023, A121024, A121025, A121026, A121027, A121028, A121029, A121030, A121032, A121033, A121034, A121035, A121036, A121037, A121038, A121039, A121040.
%K A121031 nonn,base,easy
%O A121031 1,1
%A A121031 _Reinhard Zumkeller_, Jul 21 2006