■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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