2. Amicable numbers

Search program for amicable numbers

Using fnSigma(N) subroutine, we try to find amicable numbers up to smaller number less than 10¹⁰.

 10   '
 20   for M=2 to 10^9
 30     N=fnSigma(M)-M:if N<=M then 50
 40     R=fnSigma(N)-N:if R=M then print M,N
 50   next M
 60   end
 70   fnSigma(N)
 80   local W,S,P
 90   S=1
100   W=1:P=prmdiv(N)
110   if N@P=0 then W=W*P+1:N=N\P:goto 110 else S=S*W
120   if N>1 then 100 else return(S)

The "if" condition in the line 30 is the rule for omitting perfect numbers.
 
There are 1427 amicable pairs which smaller number is less than 10¹⁰.