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尤拉數En是一個整數數列,由下列泰勒級數展開式定義:

奇數項的尤拉數皆為零,偶數項的尤拉數正負相間,開首為:

E0 = 1
E2 = -1
E4 = 5
E6 = -61
E8 = 1,385
E10 = -50,521
E12 = 2,702,765
E14 = -199,360,981
E16 = 19,391,512,145
E18 = -2,404,879,675,441 (OEIS數列A028296

部份作者會把數列中的奇數項移除,只替偶數項編序,並且把負號轉為正號。這裡依從上段所用的慣例。

尤拉數在正割sec x雙曲正割sech x泰勒級數出現。雙曲正割就是定義中使用的函數。組合數學也會用到尤拉數。此外,在關於自然數負冪的交錯和中也涉及到尤拉數。

尤拉多項式是以尤拉數構造。

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