Results on the resummation of non-power-series expansions of the Adler function of a scalar, D S , and a vector, D V , correlator are presented within fractional analytic perturbation theory (FAPT). The first observable can be used to determine the decay width Γ H→bb of a scalar Higgs boson to a bottom-antibottom pair, while the second one is relevant for the e + e − annihilation cross section. The obtained estimates are compared with those from fixed-order (FOPT) and contour-improved perturbation theory (CIPT), working out the differences. We prove that although FAPT and CIPT are conceptually different, they yield identical results. The convergence properties of these expansions are discussed and predictions are extracted for the resummed series of R S and D V using one-and two-loop coupling running, and making use of appropriate generating functions for the coefficients of the perturbative series.Since the original work of Shirkov and Solovtsov [1] appeared in 1997, the analytic approach to QCD perturbation theory has evolved and progressed considerably. At the heart of this approach is the spectral density which provides the means to define an analytic running coupling in the Euclidean space via a dispersion relation in accordance with causality and renormalization-group (RG) invariance. Using the same spectral density one can also define the running coupling in Minkowski space by employing the dispersion relation for the Adler function [2][3][4][5]. In parallel, this approach has been extended beyond the one-loop level [5,6] and analytic and numerical tools for its application have been developed [7][8][9][10][11][12]. These efforts culminated in a systematic calculational framework, termed Analytic Perturbation Theory (APT), recently reviewed in [13].The simple analytization of the running coupling and its integer powers has been generalized to the level of hadronic amplitudes [14,15] as a whole and new techniques have been developed to deal with more than one (large) momentum scale [16][17][18] (for a brief exposition, see [19]). This encompassing version of analytization includes all terms that may contribute to the spectral density, i.e., affect the discontinuity across the cut along the negative real axis −∞ < Q 2 < 0. It turns out that logarithms of the second large scale, which can be the factorization scale in higher-order perturbative calculations or the evolution scale, correspond to non-integer indices of the analytic couplings, giving rise-in Euclidean space-to Fractional Analytic Perturbation Theory (FAPT) [20,21]. This concept was successfully extended to the timelike region and a unified description in the whole complex momentum space was achieved [22] (see also [23,24]). The issue of crossing heavy-flavor thresholds, naturally entering such calculations, has been considered within APT [13,18,25,26] and more recently also within FAPT [27].Another important topic, which is at the core of the present investigation, deals with the perturbative summation in (F)APT. As it has been demonstrated in [2...