minecraft-src/data/minecraft/worldgen/structure_set/end_cities.json

{
  "placement": {
    "type": "minecraft:random_spread",
    "salt": 10387313,
    "separation": 11,
    "spacing": 20,
    "spread_type": "triangular"
  },
  "structures": [
    {
      "structure": "minecraft:end_city",
      "weight": 1
    }
  ]
}