21430267

Appears in sequences

• a(n) = A047098(n)/2.at n=10A047099
• Expansion of f(x^3)/(1-x*f(x^3)), where f(x) is the g.f. of A001764, whose n-th term is binomial(3n,n)/(2n+1).at n=32A126042
• Sequence h_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition).at n=21A129874