OFFSET
1,1
COMMENTS
All the terms are even. Conjecture: The sequence a(n)/2 is the complement of A157932 (verified for a(n) < 4*10^7). - Amiram Eldar, Oct 11 2023
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
18 is in the sequence since it has 2 odd and 2 even, refactorable divisors: 1, 2, 9, and 18.
MATHEMATICA
q[n_] := DivisorSum[n, (-1)^# &, Divisible[#, DivisorSigma[0, #]] &] == 0; Select[Range[2, 200, 2], q] (* Amiram Eldar, Oct 11 2023 *)
PROG
(PARI) is(n) = (n%2)! && sumdiv(n, d, (-1)^d * !(d % numdiv(d))) == 0; \\ Amiram Eldar, Oct 11 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jun 10 2021
STATUS
approved