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Category: | Series |

Submitted By: | shenqiang |

Fun: | (1.69) |

Difficulty: | (3.03) |

What's the next number in this series?

1, -6, -9, 0, 45, 198, ?

-6=1*3+(-9)

-9=-6*3+9

0=-9*3+27

45=0*3+45

198=45*3+63

-9, 9, 27, 45, 63 form an arithmetic sequence with common difference 18.

and therefore, the next number is

675=198*3+81.

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