Supermassive black hole formation via collisions in black hole clusters B. Gaete, D. R. G. Schleicher, A. Lupi, B. Reinoso, M. Fellhauer and M. C. Vergara A&A, 690 (2024) A378 Published online: 22 October 2024 DOI: 10.1051/0004-6361/202450770