A360980 a(n) is the least multiple of n that is an odious number (A000069).

1, 2, 21, 4, 25, 42, 7, 8, 81, 50, 11, 84, 13, 14, 285, 16, 289, 162, 19, 100, 21, 22, 69, 168, 25, 26, 81, 28, 87, 570, 31, 32, 1089, 578, 35, 324, 37, 38, 117, 200, 41, 42, 301, 44, 405, 138, 47, 336, 49, 50, 357, 52, 265, 162, 55, 56, 171, 174, 59, 1140, 61

Offset: 1

Author

Rémy Sigrist, Feb 27 2023

Keywords

• nonn
• base
• look

Comments

This sequence is well defined (see A178757).

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000069, A178757, A360981 (variant for evil numbers).

Programs

Maple

f:= proc(n) local k;
  for k from n by n do
    if convert(convert(k,base,2),`+`)::odd then return k fi
  od
end proc:
map(f, [$1..100]); # Robert Israel, Mar 29 2023

Mathematica

a[n_] := Module[{k = n}, While[EvenQ[DigitCount[k, 2, 1]], k +=n]; k]; Array[a, 100] (* Amiram Eldar, Aug 07 2023 *)

PARI

a(n) = { forstep (m=n, oo, n, if (hammingweight(m)%2==1, return (m))) }

Python

def A360980(n):
    k = n
    while k.bit_count()&1^1:
        k += n
    return k # Chai Wah Wu, Feb 28 2023

Formula

a(n) = A178757(n) * n.

a(n) = n iff n belongs to A000069.