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Numbers k such that Fibonacci(k) is either prime or semiprime.
1

%I #82 Feb 26 2023 20:39:59

%S 3,4,5,7,8,9,10,11,13,14,17,19,22,23,26,29,31,34,41,43,47,53,59,61,71,

%T 73,79,83,89,94,101,107,109,113,121,127,131,137,151,167,173,191,193,

%U 199,227,251,271,277,293,331,353,359,397,401,431,433,449,467,509,569,571,587,599,601,613,631,653,743,991,1091,1223,1373,1487

%N Numbers k such that Fibonacci(k) is either prime or semiprime.

%C Numbers k such that 2 <= A063375(k) <= 4.

%C All numbers in the first 4 rows of A279021 are in this sequence (3, 5, 11, 17, 353, 431, 509, and 587).

%C Are all numbers of A279021 in this sequence?

%F A001605 U A072381.

%Y Cf. A000045, A001605, A063375, A072381, A136341, A279021.

%K nonn

%O 1,1

%A _Bobby Jacobs_, Jan 04 2017

%E a(31)-a(64) from _Charles R Greathouse IV_, Jan 04 2017

%E a(65)-a(73) from _Max Alekseyev_, Feb 26 2023