Here is a zoom out by a factor of two from yesterday’s picture. The triangular shape at the top is called a Tricorn or Mandelbar. The parameter a is 2.5. (See Bugs #8 for a description of the formula.) The image is centered at $latex (a * pi /2) * i$.

The Tricorn set is generated by $latex bar{z}^2+c$. The standard formula is modified to use the complex conjugate of z. Here is a non-paywall academic paper on Tricorns