A356876 Binary weight of the composite numbers (A002808).

1, 2, 1, 2, 2, 2, 3, 4, 1, 2, 2, 3, 3, 2, 3, 3, 4, 3, 4, 1, 2, 2, 3, 2, 3, 4, 2, 3, 3, 4, 4, 2, 3, 3, 4, 3, 4, 5, 3, 4, 4, 4, 5, 6, 1, 2, 2, 2, 3, 3, 2, 3, 4, 3, 4, 4, 2, 3, 3, 3, 4, 4, 5, 3, 4, 5, 4, 5, 5, 6, 2, 3, 4, 3, 4, 3, 4, 4, 4, 5, 6, 3, 4, 5, 4, 5, 5, 6, 4, 5, 5

Offset: 1

Author

Karl-Heinz Hofmann, Oct 02 2022

Keywords

• base
• nonn
• easy

Links

• Karl-Heinz Hofmann, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002808, A000120, A014499.

Programs

Mathematica

DigitCount[#, 2, 1] & /@ Select[Range[125], CompositeQ] (* Amiram Eldar, Oct 03 2022 *)

PARI

forcomposite (k=0, 120, print1 (hammingweight(k),", ")) \\ Hugo Pfoertner, Oct 03 2022

Python

from sympy import isprime
print([bin(k)[2:].count("1") for k in range(4, 123) if not isprime(k)])

Formula

a(n) = A000120(A002808(n)).