Project Euler: problem 2

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

# Inititae a vector x with two values 1 and 2, the starting points for the Fibonacci series 

x <- c(1,2)

length(x)

# Take an object "i", with a starting value of 1. 
# This object will be used to as an index for the vector "x". 
# We continue to add# the (n - 1)^th term  and the (n - 2)^th term
# to get the n^th term. 

# This process continues as long as an element of vector x with 
# index value "i" just crosses the 4,000,000 mark.

i <- 1

while (x[i] < 4000000){i <- i + 1

                        x.index <- length(x)

                        x[x.index + 1] <- x[x.index] + x[x.index - 1]}

x

# Sum the even values of the Fibonacci series thus obtained

sum(x[x %% 2 == 0])


Answer : 4613732