1,2

Begin with the main tree A183079 generated by the triangular numbers:

......................1

......................2

.............3.................4

.........6.......5........10........7

.......21..9...15..8....55..14....28..11

Every n>2 is in the subtree from 3 or the subtree from 4.

Therefore, on subtracting 2 from all entries of those subtrees, we obtain complementary trees: A183231 and A183232.

Table of n, a(n) for n=1..48.

See the formulas at A183079 and A183233.

First three levels:

............1

.......4.........3

....19...7.....13..6

Cf. A183079, A183232 (second tree), A183233.

Sequence in context: A276083 A161893 A192773 * A241358 A178417 A178628

Adjacent sequences: A183228 A183229 A183230 * A183232 A183233 A183234

nonn,tabf

Clark Kimberling, Jan 02 2011

approved