login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A328012 Numbers whose binary representations start and end with 1 and contain an even number of zeros between. 1
1, 3, 7, 9, 15, 19, 21, 25, 31, 33, 39, 43, 45, 51, 53, 57, 63, 67, 69, 73, 79, 81, 87, 91, 93, 97, 103, 107, 109, 115, 117, 121, 127, 129, 135, 139, 141, 147, 149, 153, 159, 163, 165, 169, 175, 177, 183, 187, 189, 195, 197, 201, 207, 209, 215, 219, 221, 225 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Odd members of A059010. - Robert Israel, Nov 30 2019

LINKS

Jonathan Frech, Table of n, a(n) for n = 1..10000

MAPLE

q:= n-> (l-> l[1]=1 and add(1-i, i=l)::even)(Bits[Split](n)):

select(q, [$1..300])[];  # Alois P. Heinz, Oct 04 2019

MATHEMATICA

{1}~Join~Select[Range[3, 225, 2], EvenQ@ DigitCount[#, 2, 0] &] (* Michael De Vlieger, Oct 05 2019 *)

PROG

(PARI) ok(n)={n%2 && hammingweight((2<<logint(n, 2)) - 1 - n)%2==0} \\ Andrew Howroyd, Oct 01 2019

(Python)

n, a = 0, 1

while n < 58:

    aa, k = a, 0

    while aa > 0:

        d, aa = aa%2, aa//2

        if d == 0:

            k = k+1

    if k%2 == 0:

        n = n+1

        print(n, a)

    a = a+2 # A.H.M. Smeets, Oct 04 2019

CROSSREFS

Cf. A023416, A059010.

Sequence in context: A187108 A026175 A026139 * A292911 A119681 A197625

Adjacent sequences:  A328009 A328010 A328011 * A328013 A328014 A328015

KEYWORD

nonn,base

AUTHOR

Justin Clifton, Oct 01 2019

EXTENSIONS

More terms from Alois P. Heinz, Oct 04 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 13 09:12 EDT 2021. Contains 342935 sequences. (Running on oeis4.)