2,2

R. K. Guy, A quarter century of "Monthly" unsolved problems, 1969-1993, Amer Math. Monthly, 100 (1993), 945-949.

R. K. Guy, Unsolved Problems in Number Theory, Sect. C10.

J. Leech, On the representation of $1,2,\cdots,n$ by differences. J. London Math. Soc. 31 (1956), 160-169.

Index entries for sequences related to trees

Cf. A005488.

Sequence in context: A133205 A049991 A031940 this_sequence A082004 A112773 A070885

Adjacent sequences: A007184 A007185 A007186 this_sequence A007188 A007189 A007190

nonn,hard,nice

njas

a(11)>=48, a(12)>=55.