CatalanSequence.cs

usingSystem.Collections.Generic;
usingSystem.Numerics;

namespaceAlgorithms.Sequences;

/// <summary>
/// <para>
/// Catalan numbers: C[n+1] = (2*(2*n+1)*C[n])/(n+2).
/// </para>
/// <para>
/// Wikipedia: https://en.wikipedia.org/wiki/Catalan_number.
/// </para>
/// <para>
/// OEIS:http://oeis.org/A000108.
/// </para>
/// </summary>
publicclassCatalanSequence:ISequence
{
/// <summary>
/// Gets sequence of Catalan numbers.
/// </summary>
publicIEnumerable<BigInteger>Sequence
{
get
{
// initialize the first element (1) and define it's enumerator (0)
varcatalan=newBigInteger(1);
varn=0;
while(true)
{
yieldreturncatalan;
catalan=(2*(2*n+1)*catalan)/(n+2);
n++;
}
}
}
}