Find the Fibonacci Sequence

A Fibonacci sequence is the integer sequence of 0, 1, 1, 2, 3, 5, 8.... The first two terms are 0 and 1. All other terms are obtained by adding the preceding two terms. This means to say the nth term is the sum of (n-1)th and (n-2)th term.

Source Code

# Program to diplay the fibonacci
# sequence up to n-th tern where
# n is provided by the user

# take input from the user
nterms = as.integer(readline(prompt="How many terms? "))

# first two terms
n1 = 0
n2 = 1
count = 2

# check if the number of terms is valid
if(nterms <= 0) {
    print("Plese enter a positive integer")
} else {
    if(nterms == 1) {
        print("Fibonacci sequence:")
        print(n1)
    } else {
        print("Fibonacci sequence:")
        print(n1)
        print(n2)
        while(count < nterms) {
            nth = n1 + n2
            print(nth)
            # update values
            n1 = n2
            n2 = nth
            count = count + 1
        }
    }
}

Output

How many terms? 7
[1] "Fibonacci sequence:"
[1] 0
[1] 1
[1] 1
[1] 2
[1] 3
[1] 5
[1] 8 

Here, we ask the user for the number of terms in the sequence. We initialize the first term to 0 and the seconde term to 1. If the number of terms is more than 2, we use a while loop to find the next term in the sequence by adding the preceding two terms. We then interchange the variables (update it) and continue on with the process.