# Partial Sums

by brusier
Tags: partial, sums
 P: 352 Rather than applying formulas, you need to stop and think for a second. What does it mean that $$a_n$$ is the $$n$$th digit after the decimal point in the decimal expansion of $$2\pi + 2e$$ ? What is a decimal expansion? What is $$1 \cdot (0.1)^1 + 4 \cdot (0.1)^2 + 1 \cdot (0.1)^3 + 5 \cdot (0.1)^4 + 9 \cdot (0.1)^5$$?