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1) 2 is not a factor of n. So n is odd. n=1, r =0; n=3, r=8. Insufficient
2) 3 is not a factor of n. So either (n-1) or (n+1) has a factor of 3. n=1, r=0; n=4, r= 15. Insufficient.
1) and 2). So n is odd and n is not a factor of 3. If so, 1) both n-1 and n+1 are even; 2) one of them has a factor of 4; 3) one of them has a factor of 3. So n=2*4*3*m = 24*m. r=0. Sufficient.
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