c A071912 Compute mmm terms (set mmm in line 4) implicit integer(a-z) integer a(0:10000) mmm=100 a(0)=0 a(1)=1 a(2)=1 do 10 n=3,mmm c look for a(n) n1=a(n-1) if(n1.eq.1)goto 11 c try going down do 12 i=n1,1,-1 j=ngcd(n1,i) if(j.gt.1)goto 12 c is (n1,i) new? do 15 i2=0,n-2 if(a(i2).eq.n1.and.a(i2+1).eq.i)goto 12 15 continue c yes OK! a(n)=i goto 10 12 continue c didn't find it 11 continue c must go up do 14 i=n1+1,100000 j=ngcd(n1,i) if(j.gt.1)goto 14 c is (n1,i) new? do 17 i2=0,n-2 if(a(i2).eq.n1.and.a(i2+1).eq.i)goto 14 17 continue c yes OK! a(n)=i goto 10 14 continue c didn't find it write(*,*)"ERROR 1" 10 continue c print write(*,100)(a(i),i=0,mmm) 100 format(15i5) stop end c simple gcd 7.1.87 function ngcd(m,n) if(m.ne.0)goto 70 ngcd=iabs(n) return 70 if(n.ne.0)goto 71 ngcd=iabs(m) return 71 m1=iabs(m) n1=iabs(n) ngcd=n1 2 nr=mod(m1,ngcd) if(nr.eq.0)return m1=ngcd ngcd=nr goto 2 end