This block displays some visual variations on the Recamán sequence. Inspiration comes from the Numberphile‘s video The Slightly Spooky Recamán Sequence.
Here is how the Recamán sequence is computed :
a(0) = 0;
for n > 0:
a(n) = a(n-1) - n if positive and not already in the sequence,
a(n) = a(n-1) + n otherwise
Technically speaking, this block allows me to experiment path animation with CSS.