OFFSET
1,2
COMMENTS
See A343651 for the corresponding divisors.
LINKS
FORMULA
EXAMPLE
For n = 18:
- we have the following divisors:
d 18/d bin(d) bin(18/d) Requires carries?
-- ---- ------ --------- -----------------
1 18 1 10010 No
2 9 10 1001 No
3 6 11 110 Yes
6 3 110 11 Yes
9 2 1001 10 No
18 1 10010 1 No
- so a(18) = #{1, 2, 9, 18} = 4.
PROG
(PARI) a(n, h=hammingweight) = my (hn=h(n)); sumdiv(n, d, hn==h(d)*h(n/d))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Apr 24 2021
STATUS
approved