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 A385663 #32 Jul 28 2025 20:07:29 %S A385663 0,11,101,110,1001,1010,1100,1111,10001,10010,10100,10111,11000,11011, %T A385663 11101,11110,100001,100010,100100,100111,101000,101011,101101,101110, %U A385663 110000,110011,110101,110110,111001,111010,111100,111111,1000001,1000010,1000100,1000111 %N A385663 Binary numbers with an even number of 1s. %H A385663 David Consiglio, Jr., <a href="/A385663/b385663.txt">Table of n, a(n) for n = 1..10001</a> %F A385663 a(n) = A007088(A001969(n)). - _Michael S. Branicky_, Jul 23 2025 %o A385663 (Python) %o A385663 def a(n): return int(bin(((n-1)<<1)|((n-1).bit_count()&1))[2:]) %o A385663 print([a(n) for n in range(1, 37)]) # _Michael S. Branicky_, Jul 23 2025 %Y A385663 Cf. A007088, A001969. %K A385663 nonn,base,easy %O A385663 1,2 %A A385663 _Matthew Schulz_, Jul 06 2025 %E A385663 More terms from _David Consiglio, Jr._, Jul 23 2025 %E A385663 Offset changed to 1 by _Michael S. Branicky_, Jul 23 2025