OFFSET
1
MAPLE
with(ListTools);
psi:=proc(S)
Flatten(subs( {0=[0, 0, 0, 1], 1=[1, 1, 1, 0]}, S));
end;
S:=[0];
for n from 1 to 6 do S:=psi(S): od:
S;
MATHEMATICA
SubstitutionSystem[{0 -> {0, 0, 0, 1}, 1 -> {1, 1, 1, 0}}, {0}, 4] // Last (* Jean-François Alcover, Jan 21 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 08 2017
STATUS
approved