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Figure 3.: Residuals of Residuals of Figure 1. [Plot avg. error bars = ± 2.05 min.]
No credible periodicities were indicated in the Lomb-Scargle Periodogram; the lowest FAP was ~ 0.66.  Although some curvature may be visually discerned in this graph, its credibility due to errors and the lack of any clear LSP periodicity is too low to consider here.

Literature Tc#, Tc, and TTV Major Tabulations and Other References (also see "Summary" page):
• Nesvorny, Kipping, & Terrell, arXiv-1405.2060, 8 May 2014.
• For Q0-6 TTV data (thru ~ 563 (BJD-2454900) days): Ford et al., 2012, arXiv-1201.1892.
• For Q0-10 TTV data (thru ~ 934 (BJD-2454900) days): Rowe et al., 2014, arXiv-1402.6534.
• For Q0-12 TTV data (thru ~ 1116 (BJD-2454900) days): Mazeh et al., 2013, arXiv-1301.5499.
• For Q0-12 Calc. properties from TTVs: Hadden & Lithwick, 2013, arXiv-1310.7942.
• For Q0-13/14 TTV data, Xie: http://www.astro.utoronto.ca/~jwxie/TTV/TTV_Home.html
• Two ground-based Kepler-TTV-follow-up programs are in place at the moment: --- Gary, "KAFO" project: http://brucegary.net/kafo/ --- von Essen, "KOINet": http://koinet.astro.physik.uni-goettingen.de/

21 May 2014
TTVs are derived from Q1-Q17 Kepler data.  x-axes: “Observed Tc” (Mid-Transit Time): EXOFAST’s best-fits from Normalized PDCSAP_FLUX Kepler light flux vs. time (BJD_tdb - 2454900) data.  y-axes: “(O – C)”: difference between Observed Tc and the Calculated Tc from the graphically obtained linear ephemeris.

Figure 1.: KOI-319.01, P = 46.15 days [Plot avg. error bars = ± 1.55 min.]
TTV_minimum: 212.66 ± 7.27 days, Amp_ttv_minimum: -11.52 ± 1.10 min.
TTV_maximum: 366.61 ± 7.64 days, Amp_ttv_maximum: 13.77 ± 1.10 min.
TTV_minimum: 520.56 ± 8.18 days, Amp_ttv_minimum: -11.52 ± 1.10 min.
TTV_maximum: 674.50 ± 8.86 days, Amp_ttv_maximum: 13.77 ± 1.10 min.
TTV_minimum: 828.45 ± 9.64 days, Amp_ttv_minimum: -11.52 ± 1.10 min.
TTV_maximum: 982.40 ± 10.50 days, Amp_ttv_maximum: 13.77 ± 1.10 min.
TTV_minimum: 1136.35 ± 11.43 days, Amp_ttv_minimum: -11.52 ± 1.10 min.
TTV_maximum: 1290.29 ± 12.41 days, Amp_ttv_maximum: 13.77 ± 1.10 min.
TTV_minimum: 1444.24 ± 13.43 days, Amp_ttv_minimum: -11.52 ± 1.10 min.
P_ttv: 307.89 ± 2.43 days.
Amp_ttv: 25.30 ± 1.55 minutes.
Lomb-Scargle periodogram, candidate P_ttv: 306.87 days; Power: 12.59; FAP: 2.043 x 10^-11.
Linear ephemeris (this work): Tc = 46.15113856(Tc#) + 109.62844070

Figure 2.: Residuals of Figure 1. [Plot avg. error bars = ± 1.90 min.]
TTV_minimum: 136.35 ± 6.64 days, Amp_ttv_minimum: -3.40 ± 0.77 min.
TTV_maximum: 190.17 ± 6.71 days, Amp_ttv_maximum: 3.16 ± 0.77 min.
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
TTV_minimum: 1428.06 ± 12.09 days, Amp_ttv_minimum: -3.40 ± 0.77 min.
TTV_maximum: 1481.88 ± 12.41 days, Amp_ttv_maximum: 3.16 ± 0.77 min.
P_ttv: 107.64 ± 0.76 days.
Amp_ttv: 6.56 ± 1.09 minutes.
Lomb-Scargle periodogram, candidate P_ttv: 107.78 days; Power: 7.35; FAP: 1.068 x 10^-3.

Figure 4.: Added combination of Figures 1. and 2. [Plot error bars = ± 2.45 min.]
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Kepler KOI-319 (KIC-8684730) 3-(or more?)-Planet System

Discussion:
In this example, after a sinusoidal curve-fit of the (O-C) vs. Time data showed (Figure 1. below) a periodicity (P_ttv) of 307.89 ± 2.43 days (306.87 days was observed in the Lomb-Scargle Periodogram (LSP) of the same data), a plot (Figure 2.) of the Residuals also gave a good sinusoidal curve-fit with a periodicity of 107.64 ± 0.76 days (LSP: 107.78 days).  [The Residuals-of-the-Residuals (Figure 3.) showed no credible periodicity in the LSP.]  The added combination of the two sinusoidal curves is arrayed in Figure 4. and reasonably reproduces a complex overall curvature consistent with the initial data.  While it is certainly possible (see recent work of Lithwick and others) that some of this unusual curvature obtains from eccentric orbits of planetary objects in this system, it is also possible that at least 3 planets in near-circular orbits are mutually-interacting to give the TTV distribution observed.