An optimized Steffensen-type iterative method with memory associated with annuity calculation Fuad W. Khdhr, Fazlollah Soleymani, Rostam K. Saeed and Ali Akgül Eur. Phys. J. Plus, 134 4 (2019) 146 Published online: 12 April 2019 DOI: 10.1140/epjp/i2019-12665-3