A385663 Binary numbers with an even number of 1s.

0, 11, 101, 110, 1001, 1010, 1100, 1111, 10001, 10010, 10100, 10111, 11000, 11011, 11101, 11110, 100001, 100010, 100100, 100111, 101000, 101011, 101101, 101110, 110000, 110011, 110101, 110110, 111001, 111010, 111100, 111111, 1000001, 1000010, 1000100, 1000111

Offset

1,2

Links

David Consiglio, Jr., Table of n, a(n) for n = 1..10001

Formula

a(n) = A007088(A001969(n)). - Michael S. Branicky, Jul 23 2025

Prog

(Python)
def a(n): return int(bin(((n-1)<<1)|((n-1).bit_count()&1))[2:])
print([a(n) for n in range(1, 37)]) # Michael S. Branicky, Jul 23 2025

Crossrefs

Cf. A007088, A001969.

Sequence in context: A239236 A043494 A277959 * A278937 A038444 A115824

Adjacent sequences: A385660 A385661 A385662 * A385664 A385665 A385666

Keyword

nonn,base,easy

Author

Matthew Schulz, Jul 06 2025

Extensions

More terms from David Consiglio, Jr., Jul 23 2025

Offset changed to 1 by Michael S. Branicky, Jul 23 2025

Status

approved