939524094domain: NAppears in sequencesa(n) = Sum_{k=0..n} A026615(n, k).at n=29A026622a(0)=1, a(1)=2, a(2)=1; for n>2, a(n) = 7*2^(n-3)-2.at n=30A174317a(n) = 7*2^n - 2.at n=27A176448Number of acyclic edge covers of the complete bipartite graph K_{n,2}.at n=25A328890