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

1,2

Comments

This sequence is well defined (see A178757).

Links

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

Formula

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

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

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 *)

Prog

(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

Crossrefs

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

Sequence in context: A303218 A162536 A100980 * A122509 A024230 A358520

Adjacent sequences: A360977 A360978 A360979 * A360981 A360982 A360983

Keyword

nonn,base,look

Author

Rémy Sigrist, Feb 27 2023

Status

approved