Table of Reciprocal Amicable Pairs
 
    Type     Known   Last update
   Ordinary    6  7D-35D  3-Mar-2003 
   Unitary    3   8D-27D    3-Mar-2003
   -1sigma    0   0D   3-Mar-2003
   Unitary phi   40  1D-17D  3-Mar-2003 




 
 
                    click on numbers
                    Thanks to Hickerson  
 
 
  [Definition]     
 
  Reciprocal AP :
     1/sigma(a)=1/sigma(b)=1/k*(1/a+1/b)
     where if x=product p_i^r_i then sigma(x)=product (sum p_i^s_i , s_i=0 to r_i)
 
  Unitary reciprocal AP :
     1/usigma(a)=1/usigma(b)=1/k*(1/a+1/b)
     where if x=product p_i^r_i then usigma(x)=product (p_i^r_i+1)
 
  (-1)-sigma reciprocal AP :
     1/-1sigma(a)=1/-1sigma(b)=1/k*(1/a+1/b)
     where if x=product p_i^r_i then -1sigma(x)=product (-1 + sum p_i^s_i , s_i=1 to r_i)
 
  Unitary phi reciprocal AP :
     1/uphi(x)=1/uphi(y)=k*(1/x-1/y)
     where if x=product p_i^r_i then uphi(x)=product (p_i^r_i-1)
 
  Note 1 : Reciprocal AP is also represented as sigma(a)=sigma(b)=k*a*b/(a+b).
       So, it is one of the Rational APs.     
 
  Note 2 : All terms of -1sigma(x) are divisors of x, it is not the sum of divisors but
       a difference of divisors of x.
 
 
under consstruction