Factor[x^13-y^13]

f[n_] := n^2-n+41;
Table[{i, PrimeQ[f[i]]}, {i,1,41}] //MatrixForm

g[x_] := 991x^2+1

Sqrt[g[3]]

g[12055735790331359447442538767]

Sqrt[%]

seq[0]:= 0; seq[1]:= a; seq[n_] := seq[n]=1/5 seq[n-1] + 4/5 seq[n-2];

Table[seq[i], {i,0,10}]

Binomial[10,6]