SENSigma(n)=5*n where SENSigma(m) = (-1)^((Sum_i r_i)+Omega(m))*Sum_{d|m} (-1)^((Sum_j r_j)+Omega(d))*d =Product_i (Sum_{1<=s_i<=r_i} p_i^s_i)+(-1)^(r_i+1) where m=Product_i p_i^r_i, d=Product_j p_j^r_j.
SEN is for Signed by Exponents of prime factors and Number of prime factors.
For instance, SENSigma(240) = (-1+2+4+8+16)*(1+3)*(1+5) = 696.
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