641520

Appears in sequences

• A convolution triangle of numbers generalizing Pascal's triangle A007318.at n=29A049327
• a(n) = Sum_{k=0..floor(n/2)} binomial(n-k,k-1)*3^(n-k-1).at n=12A099581
• a(n) = 3a(n-1) + 3a(n-2). a(0) = 1, a(1) = 4.at n=10A125145
• Triangle read by rows: T(n,k) is the number of sequences of length n on the alphabet {0,1,2,3}, containing k subsequences 00 (0<=k<=n-1).at n=46A128235
• a(1) = 1, for n > 1: a(n) = phi(sum of the previous terms) where phi is Euler's totient function.at n=29A165931
• a(n) = binomial(n+8,8)*6^n.at n=4A172501
• Molecular topological indices of the square graphs.at n=9A192839