■ベキ和と未定係数法(その22)

S1=Σk=n(n+1)/2

S2=Σk^2=n(n+1)(2n+1)/6

S3=Σk^3=n^2(n+1)^2/4

が多くの読者にとってお馴染みの公式であろう.さらに,

S4=Σk^4=n(n+1)(2n+1)(3n^2+3n−1)/30

S5=Σk^5=n^2(n+1)^2(2n^2+2n−1)/12

S6=Σk^6=n(n+1)(2n+1)(3n^4+6n^3−3n+1)/42

S7=Σk^7=n^2(n+1)^2(3n^4+6n^3−n^2−4n+2)/24

S8=Σk^8=n(n+1)(2n+1)(5n^6+15n^5+5n^4−15n^3−n^2+9n−3)/90

と続く.

 Sk〜n^(k+1)/(k+1)

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