14.08.2013 Views

Paperfolding, Automata, and Rational Functions - Diagonals and ...

Paperfolding, Automata, and Rational Functions - Diagonals and ...

Paperfolding, Automata, and Rational Functions - Diagonals and ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

A Mahler Functional Equation<br />

Aside. Is the number 0.11011001110010011101100011001001 . . .<br />

transcendental?<br />

Now consider subtracting the spaced out sequence from the<br />

paperfolding sequence:<br />

If we denote the paperfolding sequence by f1, f2, f3, . . . then we have<br />

verified experimentally that the formal power series F (X) = P∞ h=1<br />

satisfies the functional equation F(X) − F(X 2 ) = X/(1 − X 4 ) .<br />

fhX h<br />

Once noticed, we see that this is obvious. Inserting an extra positive<br />

fold is to replace F (X) by F(X 2 ) <strong>and</strong> to add X/(1 − X 4 ). However, the<br />

infinite paperfolding sequence is invariant under the addition of a<br />

positive fold.<br />

6

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!