seriessum関数の正しい使い道を模索してみた。
f2 =pi()
「べき級数 円周率」で検索
https://www.procrasist.com/entry/pi_1 (PROCRASISTさん)
c5 =ArrayFormula((SERIESSUM(1,1,1,ROW(indirect("A1:A"&B5))^-2)*6)^0.5)
d5 =ArrayFormula(SUM((ROW(indirect("A1:A"&B5))^-2)*6)^0.5)
c6 =ArrayFormula(SERIESSUM(-1,0,1,1/(2*(ROW(indirect("A1:A"&B6))-1)+1))*4)
d6 =ArrayFormula(sum((-1)^(ROW(indirect("A1:A"&B6))-1)/(2*(ROW(indirect("A1:A"&B6))-1)+1))*4)
c7 =ArrayFormula(SERIESSUM(-1*882^-2*4^-4,0,1,FACT((ROW(indirect("A1:A"&B7))-1)*4)*(1123+21460*(ROW(indirect("A1:A"&B7))-1))*FACT(ROW(indirect("A1:A"&B7))-1)^-4/882)^-1*4)
d7 =ArrayFormula(SUM((-1)^(row(indirect("A1:A"&B7))-1)*fact(4*(row(indirect("A1:A"&B7))-1))*(1123+21460*(row(indirect("A1:A"&B7))-1))*882^-(2*(row(indirect("A1:A"&B7))-1)+1)*(4^(row(indirect("A1:A"&B7))-1)*fact(row(INDIRECT("A1:A"&B7))-1))^-4)^-1)*4
「ラマヌジャン」で検索
https://mathlog.info/articles/3583 (Mathlogさん)
c8 =ArrayFormula(seriessum(396^-4,0,1,fact(4*(row(indirect("A1:A"&B8))-1))*(fact(row(indirect("A1:A"&B8))-1))^-4*(26390*(row(INDIRECT("A1:A"&B8))-1)+1103))*2^(3/2)*99^-2)^-1
d8 =ArrayFormula(sum(fact(4*(row(indirect("A1:A"&B8))-1))*fact(row(indirect("A1:A"&B8))-1)^-4*(26390*(row(indirect("A1:A"&B8))-1)+1103)*396^(-4*(row(indirect("A1:A"&B8))-1)))*2^(3/2)*99^-2)^-1
ラマヌジャンの円周率公式c9 =ArrayFormula(12*seriessum(640320^-3,0,1,-1^(row(indirect("A1:A"&B9))-1)*fact(6*(row(indirect("A1:A"&B9))-1))*fact(3*(row(indirect("A1:A"&B9))-1))^-1*fact(row(indirect("A1:A"&B9))-1)^-3*(545140134*(row(indirect("A1:A"&B9))-1)+13591409)*640320^-(3/2)))^-1
d9 =ArrayFormula(12*sum(-1^(row(indirect("A1:A"&B9))-1)*fact(6*(row(indirect("A1:A"&B9))-1))*fact(3*(row(indirect("A1:A"&B9))-1))^-1*fact(row(indirect("A1:A"&B9))-1)^-3*(545140134*(row(indirect("A1:A"&B9))-1)+13591409)*640320^-(3*(row(indirect("A1:A"&B9))-1)+3/2)))^-1
Chudnovskyの公式
{e5:e9} =ArrayFormula(C5:C9-D5:D9)
{f5:g9} =ArrayFormula(C5:D9-$F$2)
余談1
余談2