等とう差さ級きゅう数すうとうさきゅうすうMeanings1nounarithmetic seriesMathematical term for a sequence where the difference between consecutive terms is constant. Also called 算術級数.等とう差さ級きゅう数すうの和わを求もとめる公こう式しきを覚おぼえていますか。Do you remember the formula for the sum of an arithmetic series?