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 A056533 #14 Jul 19 2015 09:03:52
%S A056533 1,3,5,9,11,17,19,25,27,35,37,43,51,57,59,69,75,83,85,97,101,113,117,
%T A056533 129,131,147,153,161,163,181,185,195,203,211,219,233,243,257,259,273,
%U A056533 275,291,307,315,321,339,341,357,369,387,389,401,417,425,437,453,465
%N A056533 Even sieve: start with natural numbers, remove every 2nd term, remove every 4th term from what remains, remove every 6th term from what remains, etc.
%H A056533 <a href="/index/Si#sieve">Index entries for sequences generated by sieves</a>
%e A056533 Start with (1,2,3,4,5,6,7,8,9,10,11,12,....), remove every 2nd term to get (1,3,5,7,9,11,...), remove every 4th term to get (1,3,5,9,11,...), etc.
%t A056533 lst = Range@480; i = 2; While[i <= (len = Length[lst]), lst = Drop[lst, {i, len, i}]; i+=2]; lst (* _Robert G. Wilson v_, May 26 2006 *)
%Y A056533 After k-th round of sieve, A001147(k)/A000165(k) of natural numbers remain, declining slowly to zero.
%K A056533 nonn
%O A056533 1,2
%A A056533 _Henry Bottomley_, Jun 19 2000