(This article was first published on

**We think therefore we R**, and kindly contributed to R-bloggers)*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)

# to get the n

# 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.

# 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

Answer : 4613732

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