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A340861 a(n) is the least prime of the form Sum_{1<=i<=2*n-1} prime(i+1)*prime(i+k) 1

%I

%S 83,373,1543,2393,4723,13997,18047,38039,43777,62801,56383,95803,

%T 109433,122701,173687,268973,250949,359441,363619,430589,832331,

%U 813797,932749,925273,1052719,1356499,1235821,1466519,1598507,1644497,1789391,1987849,3401831,3079553,2706679,3551921,3571741,5041723

%N a(n) is the least prime of the form Sum_{1<=i<=2*n-1} prime(i+1)*prime(i+k)

%H Robert Israel, <a href="/A340861/b340861.txt">Table of n, a(n) for n = 2..10000</a>

%e a(2) = 3*3+5*5+7*7 = 83 is prime.

%e a(3) = 3*3+5*5+7*7+11*11+13*13 = 373 is prime.

%e a(4) = 3*7+5*11+7*13+11*17+13*19+17*23+19*29 = 1543 is prime.

%p f:= proc(n) local B,C,i,k,t;

%p B:= [seq(ithprime(i),i=2..2*n)];

%p C:= [seq(ithprime(i),i=1..2*n-1)];

%p for k from 1 do

%p t:= add(B[i]*C[i],i=1..2*n-1);

%p if isprime(t) then return t fi;

%p C:= [op(C[2..-1]),nextprime(C[-1])];

%p od

%p end proc:

%p map(f, [$2..100]);

%K nonn

%O 2,1

%A _J. M. Bergot_ and _Robert Israel_, Jan 24 2021

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Last modified June 12 12:58 EDT 2021. Contains 344947 sequences. (Running on oeis4.)