a := (1+ Sqrt[5])/2;

f[x_]:= a^(2*x)*Exp[-a^x];

f[1]

Sum[f[i],{i,1}]

Evaluate[f[1]]

N[f[1]]

Sum[N[f[i]],{i,3}]

l :={};

For[i=0,i<20,i++, AppendTo[l,N[f[i]]]];

ListPlot[l]

Clear[l];

Plot[f,{0,20}]

Plot[f[x],{x,0,20}]

lsum :={};

For[k=1,k<30,k++, AppendTo[lsum, Sum[N[f[i]],{i,k}]]];

ListPlot[lsum]

N[Exp[-1]*2/N[Log[a]]]

fiboseq[n_]:= fiboseq[n-1]+fiboseq[n-2];

fiboseq[1]=1;

fiboseq[2]=1;

fiboseq[3]

exsum:={};

For[k=1,k<30,k++, AppendTo[exsum, Sum[N[fiboseq[i]^2*Exp[-fiboseq[i]]],{i,k}]]];

ListPlot[exsum]

exsum[[28]]

N[1/Log[a]]

lsum2:={};

For[k=1,k<30,k++, AppendTo[lsum2, Sum[N[f[i-1]],{i,k}]]];

ListPlot[lsum2]

lsum2[[28]]

f2[x_,g_]:= a^(2*x)*Exp[-g*a^x];

lsum3:={};

For[k=1,k<30,k++, AppendTo[lsum3, Sum[N[f2[i-1,0.25]],{i,k}]]];

ListPlot[lsum3]

N[16/Log[a]]

(*jhkjh*)
f[v_]:= v+1;

toto[x_]:= If[x<1,1,3];

toto[0]

toto[5]

t={1,2,3}

t+4

Log[t]

Clear[t]

t2={1,2,3,-8}

Abs[t2]

matri:=SparseArray[{Band[{2,1}]->-1,Band[{1,1}]->3,Band[{1,2}]->-1},6];

matri //MatrixForm

vep = Eigenvectors[matri]

vep[[2,2]]

t3 = {1,2,3,4,5}

Take[t3,2]

t3

Take[t3,-2]

t3

Length[t3]