OFFSET
1,1
COMMENTS
All terms are odd.
The first term that is a square is a(241) = 49729 = 223^2.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3) = 871 because 871 = 13 * 67,
2 * 871 - 3 = 1739 = 37 * 47,
2 * 871 + 3 = 1745 = 5 * 349,
3 * 871 - 2 = 2611 = 7 * 373, and
3 * 871 + 2 = 2615 = 5 * 523 are all semiprimes.
MAPLE
filter:= m -> andmap(t -> numtheory:-bigomega(t)=2, [m, 2*m-3, 2*m+3, 3*m-2, 3*m+2]):
select(filter, [seq(i, i=1..20000, 2)]);
MATHEMATICA
s = {}; Do [ If [ {2, 2, 2, 2, 2} == PrimeOmega [{m, 2*m - 3, 2*m
+ 3, 3*m - 2, 3*m + 2}], AppendTo [s, m]], {m, 5, 10^4, 2}]; s
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov and Robert Israel, Apr 15 2025
STATUS
approved
