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A360741
Semiprimes of the form k^2 + 4.
1
4, 85, 365, 445, 533, 629, 965, 1685, 1853, 2605, 2813, 3029, 3973, 4765, 5045, 5629, 5933, 6245, 6893, 8285, 8653, 11029, 11453, 11885, 12773, 14165, 15133, 16645, 17165, 17693, 20453, 21029, 22205, 22805, 23413, 24653, 27229, 29245, 29933, 30629, 32765, 34229
OFFSET
1,1
COMMENTS
A242332 gives the corresponding values of k.
Except for 4, all terms == 5 (mod 8). - Robert Israel, Feb 18 2023
FORMULA
a(n) = A242332(n)^2 + 4.
EXAMPLE
85 is a term because 9^2 + 4 = 85 = 5*17.
MAPLE
select(t -> numtheory:-bigomega(t)=2, [seq(i^2+4, i=0..1000)]); # Robert Israel, Feb 18 2023
MATHEMATICA
Select[Range[0, 200]^2 + 4, PrimeOmega[#] == 2 &] (* Amiram Eldar, Feb 18 2023 *)
KEYWORD
nonn,easy
AUTHOR
Elmo R. Oliveira, Feb 18 2023
STATUS
approved