A377184 - OEIS

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A377184

Numbers k such that L(k)+1 is prime, where L(k) is the k-th Lucas number.

%I #21 Nov 29 2024 21:41:30

%S 0,1,3,6,18

%N Numbers k such that L(k)+1 is prime, where L(k) is the k-th Lucas number.

%C Positive terms must be a power of 3 or twice a power of 3. All other terms have trivial factors. No other terms under 10^7 (a(6) > 10^7).

%e 18 is a term because L(18)+1 = 5779 which is prime. Also 18 = 2*3^2.

%Y Indices of primes in A001612.

%Y Cf. A000032, A000204, A001606.

%K nonn,more

%O 1,3

%A _Harsh Aggarwal_, Oct 18 2024