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A293811
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"Look twice to the left" sequence starting with 1,2 (see comment).
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1
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1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1
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OFFSET
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1,2
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COMMENTS
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Stage 0: we start from 1,2.
Stage 1: we add 2 copies of the block to the left of the last term (here the block 1) giving 1,2,1,1.
Stage 2: we add 2 copies of the block to the left of the last term (here the block 1,2,1) giving 1,2,1,1,1,2,1,1,2,1.
Stage 3: we add 2 copies of the block to the left of the last term (here the block 1,2,1,1,1,2,1,1,2) giving 1,2,1,1,1,2,1,1,2,1,1,2,1,1,1,2,1,1,2,1,2,1,1,1,2,1,1,2.
Iterate the process.
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LINKS
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MATHEMATICA
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Nest[Join[#, Flatten@ ConstantArray[Take[#, Length@ # - 1], 2]] &, {1, 2}, 5] (* Michael De Vlieger, Oct 16 2017 *)
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PROG
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(PARI) v=[1, 2]; for(n=1, 10, l=length(v); w=vector(l-1, i, v[i]); v=concat(v, concat(w, w))); a(n)=v[n];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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