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A339307 Numbers k such that A228553(k) is prime. 2

%I #19 Feb 06 2021 22:00:48

%S 11,20,24,27,32,35,37,38,68,74,78,79,82,96,98,101,103,122,137,149,161,

%T 188,209,218,239,249,258,276,293,321,325,333,363,365,372,433,445,449,

%U 499,535,567,568,580,588,594,595,622,644,656,663,666,682,688,693,721,742,754,756,760,796,814,845

%N Numbers k such that A228553(k) is prime.

%H Robert Israel, <a href="/A339307/b339307.txt">Table of n, a(n) for n = 1..5000</a>

%e a(3) = 24 is in the sequence because A228553(24) = 1987 is prime.

%p f:= proc(n)

%p local S;

%p S:= select(t -> isprime(t) and isprime(2*n-t), [seq(i,i=3..n,2)]);

%p add(t*(2*n-t),t=S)

%p end proc:

%p f(2):= 4:

%p select(isprime@f, [$1..1000]);

%Y Cf. A228553, A339309.

%K nonn

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Nov 29 2020

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)