3,3

S. A. Burr, in The Mathematical Gardner, Ed. D. A. Klarner, p. 94, Wadsworth, 1981.

S. A. Burr, B. Gr\"{u}nbaum and N. J. A. Sloane, The Orchard Problem, Geometriae Dedicata, 2 (1974), 397-424.

H. E. Dudeney, Amusements in Mathematics, Nelson, London, 1917, page 56.

M. Gardner, Time Travel and Other Mathematical Bewilderments. Freeman, NY, 1988, Chap. 22.

B. Gr\"{u}nbaum, Arrangements and Spreads. American Mathematical Society, Providence, RI, 1972, p. 22.

S. A. Burr, B. Gr\"{u}nbaum and N. J. A. Sloane, The Orchard Problem, Geometriae Dedicata, 2 (1974), 397-424.

N. J. A. Sloane, Illustration of initial terms (from Gruenbaum-Burr-Sloane paper)

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Link to the result [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Nov 20 2008]

Cf. A006065, A008997, A058212.

Adjacent sequences: A003032 A003033 A003034 this_sequence A003036 A003037 A003038

Sequence in context: A047510 A071260 A026407 this_sequence A094453 A026398 A070119

nonn,nice,hard

njas

13 and 14 trees result from Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Nov 20 2008