Overview of 11.5

#5

a[n_]:=1/(2n+1)
ListPlot[a[Range[10]],Filling->Axis,PlotStyle->{Thick,PointSize[Large]}]

#13

a[n_]:=Exp[2/n]
ListPlot[a[Range[10]],Filling->Axis,PlotStyle->{Thick,PointSize[Large]}]

#17

a[n_]:=Sin[Pi/n]
ListPlot[a[Range[25]],Filling->Axis,PlotStyle->{Thick,PointSize[Large]}]

#23

b[n_]:=1/n^6
a[n_]:=(-1)^(n-1)*b[n]
ListPlot[b[Range[25]],Filling->Axis,PlotStyle->{Thick,PointSize[Large]}]
n=Ceiling[(1/.00005)^(1/6)]
S5=N[Total[a[Range[5]]]]

N[a[5]]
N[a[6]]