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%I #10 Oct 20 2022 16:26:22
%S 0,0,2,0,0,5,3,7,12,12,30,51,75,139,232,365,640,1029,1717,2872,4789,
%T 7996,13338,22288,36896,61942,102746,170993,286029,476053,793800
%N Number of vertex labels congruent to 1 modulo 3 of level n of the irregular triangle A324246.
%C a(n) is also the number of vertex labels congruent to 3 modulo 6 of row n of the irregular triangle A324038.
%C 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.
%F 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.
%Y Cf. A324038, A324039, A324246.
%K nonn,easy
%O 0,3
%A _Nicolas Vaillant_, Philippe Delarue, _Wolfdieter Lang_, May 09 2019