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We present a measurement of the fraction of inclusive W+jets events produced with net charm quantum number ±1, denoted W+c-jet, in pp collisions at √s = 1.96 TeV using approximately 1 fb-1 of data collected by the D0 detector at the Fermilab Tevatron Collider. We identify the W+jets events via the leptonic W boson decays. Candidate W+c-jet events are selected by requiring a jet containing a muon in association with a reconstructed W boson and exploiting the charge correlation between this muon and W boson decay lepton to perform a nearly model-independent background subtraction. We measure the fraction of W+c-jet events in the inclusive W+jets sample for jet pT > 20 GeV and pseudorapidity |η| < 2.5 to be 0.074±0.019(stat.)±0.012 0.014 (syst.), in agreement with theoretical predictions. The probability that background fluctuations could produce the observed fraction of W+c-jet events is estimated to be 2.5 × 10-4, which corresponds to a 3.5 σ statistical significance.