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a(n) = prime(2n-1) mod prime(n).
1

%I #10 Sep 08 2022 08:44:46

%S 0,2,1,3,1,5,7,9,13,9,11,9,15,17,15,21,19,27,23,25,33,33,31,33,33,31,

%T 35,43,51,51,29,45,39,53,49,51,53,53,55,55,61,69,57,63,67,69,65,53,55,

%U 65,81,85,89,85,85,81,79,89,89,91,95,91,77,87,101,105,89,87

%N a(n) = prime(2n-1) mod prime(n).

%H G. C. Greubel, <a href="/A022458/b022458.txt">Table of n, a(n) for n = 1..10000</a>

%t Table[Mod[Prime[2n-1],Prime[n]],{n,70}] (* _Harvey P. Dale_, Aug 10 2012 *)

%o (PARI) for(n=1,50, print1(prime(2*n-1) % prime(n), ", ")) \\ _G. C. Greubel_, Feb 28 2018

%o (Magma) [NthPrime(2*n-1) mod NthPrime(n): n in [1..50]]; // _G. C. Greubel_, Feb 28 2018

%K nonn

%O 1,2

%A _Clark Kimberling_