OFFSET
1,2
COMMENTS
That is, there is a single prime p, such that p+n and p-n are both semiprime.
Subsequence of A256389.
FORMULA
Conjecture: a(n) = A001359(n)-2. - Benedict W. J. Irwin, Apr 26 2016
EXAMPLE
A256381 is the list of numbers n such that n-3 and n+3 are semiprimes, and it contains a single prime, hence 3 is in the sequence.
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Mar 27 2015
STATUS
approved