OFFSET
1,1
COMMENTS
Non-Chen semiprimes: semiprimes m such that m+4 is neither a prime or a semiprime.
PROG
(Python)
from sympy.ntheory.factor_ import primeomega, isprime
def issemiprime(n): return primeomega(n) == 2
def ok(n): return issemiprime(n) and not (issemiprime(n+4) or isprime(n+4))
print(list(filter(ok, range(1, 472)))) # Michael S. Branicky, Apr 14 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Aug 08 2010
EXTENSIONS
Corrected (234 replaced by 254, 471 inserted) by R. J. Mathar, Aug 10 2010
STATUS
approved