[seqfan] Anyone have a 3-D "Ulam" spiral?

Neil Sloane njasloane at gmail.com
Mon Apr 26 07:02:48 CEST 2021

Dear Sequence Fans,
In two dimensions there is an obvious way to number the cells of the square
grid starting at the origin and going around in what is often called the
square spiral (aka Ulam spiral).  It visits every square once and gradually
works its way outwards.  Is there a nice analog in 3D?

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