OFFSET
1,1
COMMENTS
That is, there is no prime p, such that p+n and p-n are both semiprime.
Complement of A256389.
From Robert Israel, Apr 13 2020: (Start)
Includes odd number n if and only if n+4 is not prime or 2*n+4 is not a semiprime.
There any no even members up to 10^5. Conjecture: all members are odd. (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
A256383 is the list of numbers n such that n-5 and n+5 are semiprimes, and it contains no prime, hence 5 is in the sequence.
MAPLE
select(t -> not isprime(t+4) or numtheory:-bigomega(2*t+4) <> 2, [seq(i, i=1..1000, 2)]); # Robert Israel, Apr 13 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Mar 27 2015
STATUS
approved