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A324040
Number of vertex labels congruent to 1 modulo 3 of level n of the irregular triangle A324246.
3
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.
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
KEYWORD
nonn,easy
AUTHOR
Nicolas Vaillant, Philippe Delarue, Wolfdieter Lang, May 09 2019
STATUS
approved