OFFSET
1,1
COMMENTS
Odd numbers k that have exactly 2 divisors d such that the bitwise AND of k and d is equal to d, or equivalently, the bitwise OR of k and d is equal to k. These two divisors are 1 and k.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
q[n_] := DivisorSum[n, Boole[BitOr[#, n] == n] &] == 2; Select[Range[1, 200, 2], q]
PROG
(PARI) is(n) = n % 2 && sumdiv(n, d, bitor(d, n) == n) == 2;
(Python)
from itertools import count, islice
from sympy import divisors
def A363691_gen(startvalue=3): # generator of terms >= startvalue
return filter(lambda n:all(d==1 or d==n or n|d!=n for d in divisors(n, generator=True)), count(max(startvalue, 3)|1, 2))
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Amiram Eldar, Jun 16 2023
STATUS
approved