1905156936

Appears in sequences

• a(n) = Sum_{k=0..floor(n/2)} binomial(n-k,k-1)*3^(n-k-1).at n=18A099581
• a(n) = 3a(n-1) + 3a(n-2). a(0) = 1, a(1) = 4.at n=16A125145