10 DEFINT C,Z,N,K,M: DIM M(1000)
20 M(1)=1
30 FOR N=2 TO 1000
40 M(N)=1
50 FOR K=2 TO N: M(N) = M(N)-M(INT(N/K)): NEXT
60 NEXT
70 PRINT "First 99 Mertens numbers:"
80 PRINT "   ";
90 FOR N=1 TO 99
100 PRINT USING "###";M(N);
110 IF N MOD 10 = 9 THEN PRINT
120 NEXT
130 C=0: Z=0
140 FOR N=1 TO 1000
150 IF M(N)=0 THEN Z=Z+1: IF M(N-1)<>0 THEN C=C+1
160 NEXT
170 PRINT "M(N) is zero";Z;"times."
180 PRINT "M(N) crosses zero";C;"times."
190 END