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A256277 C(2*n,n) mod 2*n+1. 1

%I #24 Sep 08 2022 08:46:11

%S 2,1,6,7,10,1,12,1,18,19,22,6,11,1,30,9,15,1,15,1,42,15,46,29,36,1,27,

%T 55,58,1,14,19,66,21,70,1,32,35,78,43,82,40,60,1,7,60,70,1,18,1,102,

%U 96,106,1,39,1,17,96,3,111,84,31,126,84,130,37,30,1

%N C(2*n,n) mod 2*n+1.

%C a(n) == (-1)^n (mod 2*n+1) if 2*n+1 is prime or is in A163209.

%C a(n) = 0 for n in A073076.

%H Robert Israel, <a href="/A256277/b256277.txt">Table of n, a(n) for n = 1..10000</a>

%p seq(binomial(2*n,n) mod (2*n+1), n=1..100); # _Robert Israel_, Jun 12 2015

%t Table[Mod[Binomial[2 n, n], 2 n + 1], {n, 200}] (* _Vincenzo Librandi_, May 03 2016 *)

%o (Magma) [Binomial(2*n, n) mod (2*n+1): n in [1..70]]; // _Vincenzo Librandi_, May 03 2016

%Y Cf. A000984, A001405, A059288, A053214, A073076, A163209.

%K nonn

%O 1,1

%A _Robert Israel_, Jun 12 2015

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Last modified July 6 06:50 EDT 2024. Contains 374034 sequences. (Running on oeis4.)