A125685 - OEIS

%I #14 Sep 18 2024 08:29:55

%S 5,11,2,79,331,479,5297,70061,69203,8960447,45083347,1031626241,

%T 15484789693,15537907043,64166447971,3979714828967,3988907823167,

%U 27918983997629,598858179567591121853,31710728461561839214229

%N Primes in A125683(n) in order of their occurrence.

%C Corresponding numbers k such that A125683(k) is prime are listed in A125684.

%H Vincenzo Librandi, <a href="/A125685/b125685.txt">Table of n, a(n) for n = 1..65</a>

%F a(n) = A125683(A125684(n)).

%e A125683(n) begins {1,1,5,11,2,79,331,479,493,5297,2701,69071,70061,...}.

%e Thus a(1) = 5 because 5 is the first prime in A125683.

%e a(2)-a(6) = {11,2,79,331,479} because A125683(k) is prime for 3<k<9.

%t Select[Table[Numerator[Sum[(-1)^(k+1)*1/(k(k+1)), {k, 1, n}]], {n, 1, 100}], PrimeQ]

%Y Cf. A125683, A125684.

%K nonn

%O 1,1

%A _Alexander Adamchuk_, Nov 30 2006