A317295 Numbers with a composite number of 1's in their binary expansion.

15, 23, 27, 29, 30, 39, 43, 45, 46, 51, 53, 54, 57, 58, 60, 63, 71, 75, 77, 78, 83, 85, 86, 89, 90, 92, 95, 99, 101, 102, 105, 106, 108, 111, 113, 114, 116, 119, 120, 123, 125, 126, 135, 139, 141, 142, 147, 149, 150, 153, 154, 156, 159, 163, 165, 166, 169, 170, 172, 175, 177, 178, 180, 183, 184, 187, 189, 190

Offset

1,1

Comments

By definition no power of 2 is in the sequence.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

23 is in the sequence because the binary expansion of 23 is 10111 and 10111 has four 1's, and 4 is a composite number (A002808).

Mathematica

Select[Range[200], CompositeQ[DigitCount[#, 2, 1]] &] (* Amiram Eldar, Jul 23 2023 *)

Prog

(PARI) isok(n) = my(w = hammingweight(n)); (w != 1) && !isprime(w); \\ Michel Marcus, Aug 15 2018
(Python) from sympy import isprime; isok = lambda n: n & (n-1) and not isprime(bin(n).count('1')) # David Radcliffe, Aug 15 2018

Crossrefs

Complement of A317294.

Cf. A000069, A000120, A001969, A002808, A014312, A052294, A084345.

Sequence in context: A317793 A219683 A166665 * A014312 A325823 A129387

Adjacent sequences: A317292 A317293 A317294 * A317296 A317297 A317298

Keyword

nonn,base,easy

Author

Omar E. Pol, Aug 10 2018

Status

approved