A block in a graph is a maximal connected subgraph that has no cut-vertex. A complete graph having $n$ nodes is denoted by $K_n$. A block graph is a graph in which each block is a complete graph. For example in figure a block graph with blocks $K_2,K_2,K_3,K_4 $ and $K_5$. What is the number of non-isomorphic block graphs on $n$ nodes?.
1 Answer
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This appears to be http://oeis.org/A035053 . References and formulae are there.