How do I compute symbolic integrals

This is my code,I want to compute symbolic integrals,but the F1 I got is full of NAN.Why?and what should I do?

format long;

t=1:10000:8460000;

k=0.07;b=13.8'; ，

c=3e8;

v=0.062.*c;

eNi=3.9e10;

eCo=6.8e9;

tNi=8.8*86400;

tCo=111.3*86400;

M=1.9891e30;

Mej=2.1.*M;

kr=0.133;

A=(3.*kr.*Mej)/(4.*pi.*v^2);

M_Ni=0.1.*M;

tm=sqrt((2.*k.*Mej)/b.*v.*c);

P=@(x)eNi.* M_Ni.*exp(-x./tNi) + eCo.* M_Ni.*((exp(-x./tCo)-exp(-x./tNi))./(1-tNi/tCo));

f=@(x)exp(x.^2./tm^2).*x./tm.*P(x);

syms a

F=int(f,0,a);

F1=double(subs(F,a,t));

Answer 1

[madhan ravi]

Wanted=zeros(size(t)); 
for k=1:numel(t)
  Wanted(k)=integral(f,0,t(k));
end