A078039 revisited

[Meeussen Wouter (bkarnd)]

the repeated substitution
0  ->  {0,1,2}
1  ->  {0,1,2,3}
2  ->  {0,1}
3  ->  {0,1,2}
starting on list {0}
and flattening at each step
{ {sequence1}, {sequence2},..}
to {sequence1,sequence2,..}
generates a list after n steps
with length =a(n)=A078039 

with GF=       (1 - x)/(1 + x - 2*x^2 + x^3)
or, unsigned : (1 + x)/(1 - x - 2*x^2 - x^3)

Who sees the link between the substitutions
and the GF?


Wouter Meeussen









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