■サマーヴィルの等面四面体(その430)

 ハーレーの論文覚え書き.h(λ)の展開から

 Σp^2(n−p+1)^2は,p=0〜[n/2]

nが偶数のとき,(1・n)^2,{2(n−1)}^2,・・・,{n/2(n−n/2+1)}^2

nが奇数のとき,(1・n)^2,{2(n−1)}^2,・・・,{(n−1)/2(n−(n−1)/2+1)}^2

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p=0〜[n/2]のまま計算する.

Σp^2(n−p+1)^2

=(n+1)^2Σp^2−2(n+1)Σp^3+Σp^4

[1]nが偶数のとき

Σp^2(n−p+1)^2

=(n+1)^2Σp^2−2(n+1)Σp^3+Σp^4

=(n+1)^2(n/2)(n/2+1)(n+1)/6−2(n+1)(n/2)^2(n/2+1)^2/4+(n/2)(n/2+1)(n+1)(3(n/2)^2+3(n/2)−1)/30

=(n+1)^2・n(n+2)(n+1)/24−2(n+1)n^2(n+2)^2/64+n(n+2)(n+1)(3n^2+6n−4)/480

=n(n+1)(n+2)/480{20(n+1)^2−15n(n+2)+3n^2+6n−4}

=n(n+1)(n+2)/480{8n^2+16n+16}

=n(n+1)(n+2){n^2+2n+2}/60

[2]nが奇数のとき

Σp^2(n−p+1)^2

=(n+1)^2Σp^2−2(n+1)Σp^3+Σp^4

=(n+1)^2(n−1)/2{(n−1)/2+1)(n)/6−2(n+1)((n−1)/2)^2((n−1)/2+1)^2/4+(n−1)/2((n−1)/2+1)n(3(n−1)/2)^2+3(n−1)/2)−1)/30

=(n+1)^2・(n−1)(n+1)n/24−2(n+1)(n−1)^2(n+1)^2/64+(n−1)(n+1)n(3n^2−7)/480

=(n+1)(n−1)/480・{20n(n+1)^2−15(n−1)(n+2)^2+3n^3−7n}

=(n+1)(n−1){8n^3+25n^2+28n+15}/480

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