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 A371239 #10 Mar 16 2024 05:22:22 %S A371239 1,2,5,7,13,14,17,22,23,26,41,43,53,67,70,71,77,79,122,130,131,133, %T A371239 134,149,151,157,158,161,202,203,205,206,211,214,215,229,230,233,238, %U A371239 239,241,365,367,373,374,377,391,394,395,401,403,445,446,449,454,455,457 %N A371239 Squarefree numbers that are zeroless in base 3 (A032924). %C A371239 The relative asymptotic density of this sequence within the zeroless numbers in base 3 is 27/(4*Pi^2) = 1/A214549 = 0.683917... (Banks and Shparlinski, 2004). %H A371239 Amiram Eldar, <a href="/A371239/b371239.txt">Table of n, a(n) for n = 1..10000</a> %H A371239 William D. Banks and Igor E. Shparlinski, <a href="http://dx.doi.org/10.4064/aa112-4-1">Arithmetic properties of numbers with restricted digits</a>, Acta Arithmetica, Vol. 112, No. 4 (2004), pp. 313-332; <a href="https://eudml.org/doc/278042">alternative link</a>. %t A371239 Select[Range[500], !MemberQ[IntegerDigits[#, 3], 0] && SquareFreeQ[#] &] %o A371239 (PARI) is(n) = vecmin(digits(n, 3)) > 0 && issquarefree(n); %Y A371239 Intersection of A005117 and A032924. %Y A371239 Cf. A214549, A371240, A371241. %K A371239 nonn,base,easy %O A371239 1,2 %A A371239 _Amiram Eldar_, Mar 16 2024