TY - JOUR TI - Ninth-order, explicit, two-step methods for second-order inhomogeneous linear IVPs AU - Kovalnogov, V.N. AU - Simos, T.E. AU - Tsitouras, C. JO - Mathematical Methods in the Applied Sciences PY - 2020 VL - 43 TODO - 7 SP - 4918-4926 PB - John Wiley and Sons Ltd SN - 0170-4214, 1099-1476 TODO - 10.1002/mma.6246 TODO - Initial value problems, Constant coefficients; Numerical solution; Numerical tests; Numerov method; Order conditions; Second orders; Two step method; Two-step hybrid methods, Numerical methods TODO - In the present paper, the second-order linear inhomogeneous initial value problems (LI-IVP) with constant coefficients is of our interest. Two-step hybrid methods (ie, of Numerov-type) are considered for addressing this problem. Thus, a special set of order conditions is given and solved for derivation a low cost new method. Actually, we manage to save two stages per step. This is crucial as shown in various numerical tests where our new proposal outperforms standard methods in the relevant literature. © 2020 John Wiley & Sons, Ltd. ER -