OFFSET
0,4
COMMENTS
The sequence cannot contain any semiprimes.
It appears that a(n) is always even for n > 11. - Thomas Scheuerle, Feb 15 2023
LINKS
Thomas Scheuerle, Table of n, a(n) for n = 0..3999
EXAMPLE
a(0) = 1 by the definition of the sequence. For the next number we try 1; {1, 1 + 1} are not semiprimes, thus a(1) = 1. For the next number we try 1; {1, 1 + 1, 1 + 1 + 1} are not semiprimes, thus a(2) = 1.
PROG
(MATLAB)
function a = A360028(max_n)
a = 1; s = 1;
while length(a) < max_n
sn = [s+1 1];
while(~isempty(find(arrayfun(@(x)(length(factor(x))), sn)==2, 1)))
sn = sn+1;
end
s = sn; a = [a sn(end)];
end
end % Thomas Scheuerle, Jan 22 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Jan 22 2023
STATUS
approved