10 DEFINT A-Z: DIM A(100)
20 PRINT "First 15 terms:"
30 FOR N=0 TO 14: GOSUB 100: PRINT A(N);: NEXT
35 PRINT
40 PRINT "First repeated term:"
50 GOSUB 100
55 FOR M=0 TO N-1: IF A(M)=A(N) THEN 70 ELSE NEXT
60 N=N+1: GOTO 50
70 PRINT "A(";N;") =";A(N)
80 END
100 IF N=0 THEN A(0)=0: RETURN
110 X = A(N-1)-N: IF X<0 THEN 160
120 FOR M=0 TO N-1
130 IF A(M)=X THEN 160
140 NEXT
150 A(N)=X: RETURN
160 A(N)=A(N-1)+N: RETURN