Поехали.
Procedure.d BBP(n)
Protected k, sum.d = 0.0
For k = 0 To n
sum + (1.0 / Pow(16, k)) * (4.0 / (8 * k + 1) - 2.0 / (8 * k + 4) - 1.0 / (8 * k + 5) - 1.0 / (8 * k + 6))
Next
ProcedureReturn sum
EndProcedure
Debug #PI
Debug bbp(15)