OFFSET
0,1
COMMENTS
a(0) = 4. Subtracting n = 0 from a(0) gives 4-0 = 4, which is a composite number; subtracting n = 1 from a(1) gives 9-1 = 8 which is composite; subtracting n = 2 from a(2) gives 6-2 = 4 which is composite; subtracting n = 3 from a(3) gives 9-3 = 6 which is composite; etc.
PROG
(Python)
from sympy import isprime
def composite(n): return n >= 4 and not isprime(n)
def a(n):
an = n + 4
while not (composite(an) and composite(an-n)): an += 1
return an
print([a(n) for n in range(67)]) # Michael S. Branicky, Apr 09 2021
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Eric Angelini, Jan 29 2009
EXTENSIONS
More terms from Michael S. Branicky, Apr 09 2021
STATUS
approved