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20 10 Yongzhou senior high school entrance examination mathematics two questions 16 why choose 4D?
When input a=2, n(n+ 1)/2=3, then A 1 = 3, then n(n+ 1)/2=6, then A2 = 6, then N (n+/kloc)

N(n+ 1)/2 digits, so A3 = 1, input 1, n(n+ 1)/2= 1, and the subsequent results are all 1, so A206544.