A324040 Number of vertex labels congruent to 1 modulo 3 of level n of the irregular triangle A324246.

0, 0, 2, 0, 0, 5, 3, 7, 12, 12, 30, 51, 75, 139, 232, 365, 640, 1029, 1717, 2872, 4789, 7996, 13338, 22288, 36896, 61942, 102746, 170993, 286029, 476053, 793800

Offset

0,3

Comments

a(n) is also the number of vertex labels congruent to 3 modulo 6 of row n of the irregular triangle A324038.

This entry is interesting because it determines the number of vertices with out-degree 1 of level n, for n >= 1, of the modified reduced Collatz trees A324038 and A324246. All other vertices have out-degree 2. Hence this sequence determines recursively the number A324039(n) of vertices of label n of these two trees.

Links

Table of n, a(n) for n=0..30.

Formula

a(n) = 2*A324039(n) - A324039(n-1), for n >= 1, and a(0) = 0. Implied by the definition of a(n) given in the name.

Crossrefs

Cf. A324038, A324039, A324246.

Sequence in context: A369730 A156387 A370065 * A340116 A361521 A223705

Adjacent sequences: A324037 A324038 A324039 * A324041 A324042 A324043

Keyword

nonn,easy

Author

Nicolas Vaillant, Philippe Delarue, Wolfdieter Lang, May 09 2019

Status

approved