OFFSET
1,1
COMMENTS
Also, numbers with at least 1 partition into two parts (s,t), s<=t, such that s is an odd semiprime divisor of t.
LINKS
Eric Weisstein's World of Mathematics, Proper divisors
Eric Weisstein's World of Mathematics, Semiprime
EXAMPLE
18 is in the sequence since 9 | 18, and 9 is an odd semiprime < n.
30 is in the sequence since 15 | 30, and 15 is an odd semiprime < n.
MATHEMATICA
q[n_] := If[EvenQ[n], PrimeOmega[n/2^IntegerExponent[n, 2]] > 1, PrimeOmega[n] > 2]; Select[Range[200], q] (* Amiram Eldar, Jan 23 2022 *)
PROG
(PARI) isok(m) = sumdiv(m, d, if ((d<m) && (d%2), bigomega(d)==2)) > 0; \\ Michel Marcus, Jan 23 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jan 23 2022
STATUS
approved