In[]:=
ClearAll["`*"];Remove["`*"];
In[]:=
p[x_,t_]:=1-Erf[x/Sqrt[4*t]];pa[x_?NumericQ,t_?NumericQ]:=1
1/4
t
NIntegrate
HypergeometricPFQ{},
1
2
,
3
4
,-
4
s
256t

Gamma
3
4

-
sHypergeometricPFQ{},
3
4
,
5
4
,-
4
s
256t

π
1/4
t
+
2
s
HypergeometricPFQ{},
5
4
,
3
2
,-
4
s
256t

2
t
Gamma
1
4

*p[x,s],{s,0,10},Method{Automatic,"SymbolicProcessing"0},PrecisionGoal20//Quiet
In[]:=
n=5;A=ListLinePlot[Table[{t,Log[10,1-pa[1/10,10^t]]},{t,-3,8,n^-1}],AxesLabel{Log[t],Log[1-P_0.5[x,t]]},PlotRange->{Automatic,{-1.5,0}},PlotStyle->Red]
Out[]=
In[]:=
pX[x_,t_]:=1-Erf[x/Sqrt[4*t]];paX[x_?NumericQ,t_?NumericQ,m_?NumberQ]:=1
1/4
t
NIntegrate
Sum
-j
256
j
-
4
s
t
j!Pochhammer
1
2
,jPochhammer
3
4
,j
,{j,0,m}
Gamma
3
4

-
sSum
-j
256
j
-
4
s
t
j!Pochhammer
3
4
,jPochhammer
5
4
,j
,{j,0,m}
π
1/4
t
+
2
s
Sum
-j
256
j
-
4
s
t
j!Pochhammer
5
4
,jPochhammer
3
2
,j
,{j,0,m}
2
t
Gamma
1
4

*pX[x,s],{s,0,10},Method{Automatic,"SymbolicProcessing"0},PrecisionGoal20//Quiet(*Forsvalue10=Infinty!!!Form=30termsofseries*)
In[]:=
n=5;B=ListLinePlot[Table[{t,Log[10,1-paX[1/10,10^t,30]]},{t,-3,8,n^-1}],AxesLabel{Log[t],Log[1-P_0.5[x,t]]},PlotRange->{Automatic,{-1.5,0}},PlotStyle->{Black,Dashed}]
Out[]=
In[]:=
Show[{A,B}]
Out[]=