21523356

Appears in sequences

• Triangle read by rows: T(n,k) = (n+1,k)-th element of (M^9-M)/8, where M is the infinite lower Pascal's triangle matrix, 1<=k<=n.at n=38A096043
• Expansion of 3*x*(3*x+1)*(2*x-1) / ( (1+x)*(3*x^2+1) ).at n=29A143769
• a(n) = 9*(3^n - 1)/2.at n=14A168569