A075897 1 if binary weight of n is 1 or 2, otherwise 0.

0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0

Offset

0,1

Links

Table of n, a(n) for n=0..104.

Index entries for characteristic functions

Formula

a(n) = 1 if n is in A048645, 0 otherwise.

For n>0: a(n) = 0^floor(A000120(n)/3). - Reinhard Zumkeller, Apr 07 2003

Mathematica

Table[If[MemberQ[{1, 2}, Total[IntegerDigits[n, 2]]], 1, 0], {n, 0, 120}] (* Harvey P. Dale, Jul 26 2017 *)

Prog

(PARI) a(n)=(hammingweight(n)+1)\2 == 1 \\ Charles R Greathouse IV, Jan 10 2022
(PARI) a(n)=(hammingweight(n)) <= 2 && n > 0 \\ David A. Corneth, Jan 11 2022
(Python)
def a(n): return int(bin(n).count('1') in [1, 2])
print([a(n) for n in range(105)]) # Michael S. Branicky, Jan 11 2022

Crossrefs

Cf. A000120, A048645.

Sequence in context: A167393 A275606 A106549 * A135947 A360123 A211487

Adjacent sequences: A075894 A075895 A075896 * A075898 A075899 A075900

Keyword

nonn,easy

Author

Benoit Cloitre, Mar 29 2003

Status

approved