A
an bn= 2an 2bn=
n(a1+a2n−1) 2
n(b1+b2n−1) 2= A2n−1 B2n−1= 14n+34 2n+2= 7n+17 n+1=7+ 10 n+1 验证知,当n=1,4,9时 an bn为整数的正整数 故选:B
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