distribucions

f(k) = [ k // n ]·2^{(-n)}

Sum[ f(k) ] = 1

Sum[ k·f(k) ] = (n/2)

d_{x}[ (x+1)^{n} ]

Sum[ k^{2}·f(k) ] = (n/4)·(n+1)

d_{xx}^{2}[ x(x+1)^{n} ] = d_{x}[ (x+1)^{n}+xn(x+1)^{n+(-1)} ]