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A356794
Odd numbers that have at least one prime factor congruent to 1 (mod 4) and at least one prime factor congruent to 3 (mod 4).
0
15, 35, 39, 45, 51, 55, 75, 87, 91, 95, 105, 111, 115, 117, 119, 123, 135, 143, 153, 155, 159, 165, 175, 183, 187, 195, 203, 215, 219, 225, 235, 245, 247, 255, 259, 261, 267, 273, 275, 285, 287, 291, 295, 299, 303, 315, 319, 323, 327, 333, 335, 339, 345, 351
OFFSET
1,1
COMMENTS
This sequence consists of the odd positive integers that are in neither A004613 nor A004614.
EXAMPLE
15 is a term: its prime factors are 3 and 5; 3 == 3 (mod 4), 5 == 1 (mod 4).
MATHEMATICA
Select[Range[1, 351, 2], Length[Union[Mod[FactorInteger[#][[;; , 1]], 4]]] == 2 &] (* Amiram Eldar, Aug 28 2022 *)
PROG
(PARI) isok(m) = if (m % 2, my(vf=factor(m)[, 1]); (#select(x->((x%4)==1), vf) >= 1) && (#select(x->((x%4)==3), vf) >= 1)); \\ Michel Marcus, Aug 29 2022
CROSSREFS
Sequence in context: A257591 A284406 A329589 * A154988 A345331 A360110
KEYWORD
nonn
AUTHOR
Jon E. Schoenfield, Aug 27 2022
STATUS
approved