A001851 Total diameter of unlabeled trees with n nodes.

0, 1, 2, 5, 9, 21, 44, 103, 232, 571, 1368, 3441, 8653, 22263, 57518, 150733, 396937, 1054540, 2815453, 7562159, 20399714, 55280532, 150356806, 410432671, 1123902587, 3086827578, 8500975970, 23470712241, 64952794778, 180144093389

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Comments

C program around function Gen() by Gang Li & Frank Ruskey. See C program link.

Examples

			See the trees in first Bomfim link. So a(6) = 21.
		

References

• N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• W. Bomfim, Diameters of the trees of order 6
• W. Bomfim, C program
• J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478.
• J. Riordan, The enumeration of trees by height and diameter, IBM Journal 4 (1960), 473-478. (Annotated scanned copy)
• Index entries for sequences related to trees

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jul 26 2010

a(21)-a(30) from Washington Bomfim, Jan 31 2011