## 3. Quasi-amicable numbers

### Search program for quasi-amicable numbers

The definition of amicable numbers is

σ(m)-m=n

σ(n)-n=m

and the definition of quasi-amicable numbers is

σ(m)-m-1=n

σ(n)-n-1=m

or

σ(m)=σ(n)=m+n+1.

So the program can be used in trivial change,

30 N=fnSigma(M)-M:if N<=M then 50
40 R=fnSigma(N)-N:if R=M then print M,N

into

30 N=fnSigma(M)-M-1:if N<=M then 50
40 R=fnSigma(N)-N-1:if R=M then print M,N

There are **404** quasi-amicable pairs which smaller number is less than 10^{10}.

E-mail : kc2h-msm@asahi-net.or.jpHisanori Mishima