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

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, 55, 58, 1, 14, 19, 66, 21, 70, 1, 32, 35, 78, 43, 82, 40, 60, 1, 7, 60, 70, 1, 18, 1, 102, 96, 106, 1, 39, 1, 17, 96, 3, 111, 84, 31, 126, 84, 130, 37, 30, 1

Offset: 1

Author

Robert Israel, Jun 12 2015

Keywords

• nonn

Comments

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

a(n) = 0 for n in A073076.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

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

Programs

Magma

[Binomial(2*n, n) mod (2*n+1): n in [1..70]]; // Vincenzo Librandi, May 03 2016

Maple

seq(binomial(2*n,n) mod (2*n+1), n=1..100); # Robert Israel, Jun 12 2015

Mathematica

Table[Mod[Binomial[2 n, n], 2 n + 1], {n, 200}] (* Vincenzo Librandi, May 03 2016 *)