Table of n, a(n) for n=1..9.
Eric Weisstein's World of Mathematics, Molecular Topological Index
The paw graph and square graph C_4 both have MTI = 48, while all other 4-node connected simple graphs have unique MTI values, so a(4) = 2.
Sequence in context: A097237 A055531 A181345 * A059435 A192621 A143923
Adjacent sequences: A193122 A193123 A193124 * A193126 A193127 A193128
Eric W. Weisstein, Jul 16 2011