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 A208260 #15 Aug 01 2021 11:17:18
%S A208260 1,111,121,141,161,171,1001,1011,1041,1071,1081,1101,1111,1121,1131,
%T A208260 1141,1161,1191,1211,1221,1241,1251,1261,1271,1281,1311,1331,1341,
%U A208260 1351,1371,1391,1401,1411,1421,1431,1441,1461,1491,1501,1521,1541,1551,1561,1581,1591
%N A208260 Nonprime numbers starting and ending with digit 1.
%C A208260 Complement of A062332 with respect to A208259. Supersequence of A208261 (nonprime numbers with all divisors starting and ending with digit 1).
%H A208260 Reinhard Zumkeller, <a href="/A208260/b208260.txt">Table of n, a(n) for n = 1..10000</a>
%F A208260 (1 - A010051(a(n))) * A000030(a(n)) * (a(n) mod 10) = 1. - _Reinhard Zumkeller_, Jul 16 2014
%t A208260 Select[Range[2000], ! PrimeQ[#] && First[IntegerDigits[#]] == 1 && Last[IntegerDigits[#]] == 1 &] (* _Vladimir Joseph Stephan Orlovsky_, Feb 26 2012 *)
%t A208260 Join[{1},Select[Range[2000],CompositeQ[#]&&NumberDigit[#,0] == NumberDigit[ #,IntegerLength[ #]-1]==1&]] (* _Harvey P. Dale_, Aug 01 2021 *)
%o A208260 (Haskell)
%o A208260 a208260 n = a208260_list !! (n-1)
%o A208260 a208260_list = filter ((== 0) . a010051') a208259_list
%o A208260 -- _Reinhard Zumkeller_, Jul 16 2014
%Y A208260 Cf. A208259 (number starting and ending with a number 1), A062332 (primes starting and ending with a number 1).
%Y A208260 Cf. A010051, A017281, A131835, A000030.
%K A208260 nonn,base
%O A208260 1,2
%A A208260 _Jaroslav Krizek_, Feb 24 2012