an = a + (n – 1)d
等差数列の和
S = 1/2n(a + l)
等比数列
an = ar^(n-1)
等比数列和
Sn = a(1-r^n)/(1-r) = a(r^n – 1)/(r – 1)
Σ(シグマ)… 総和
π(パイ)… 総乗
数列の和
nΣk=1[k] = 1/2n(n+1)
nΣk=1[k]^2 = 1/6n(n+1)(2n+1)
nΣk=1[k]^3 = {1/2n(n+1)}^2
nΣk=1 = nc
nΣk=1(ak + bk) = nΣk=1ak + nΣk=1bk
