Out[]//TableForm=
N =
1
π ≃ 4*\*UnderoverscriptBox[\(∑\), \(n = 1\),[ToBoxes[nfin, StandardForm]​]\)\)]\)\*FractionBox[SuperscriptBox[\((\(-1\))\), \(n - 1\)]​, \(2*n - 1\)]\) = \*DynamicBox[ToBoxes[N[Sum[Times[4, Times[Power[-1, Plus[n, -1]​]​, Power[Plus[Times[2, n]​, -1]​, -1]​]​]​, List[n, 1, nfin]​]​]​, StandardForm]​]\)
Error relative to π:
0.858407