1713690

Appears in sequences

• a(n) is the number of integer strings s(0),...,s(n) counted by array T in A026374 that have s(n)=2; also a(n) = T(2n,n-1).at n=9A026376
• a(n) = Sum_{k=0..n-1} T(n,k) * T(n,k+1), with T given by A026374.at n=9A026947