Program to find Cullen Number
A Cullen Number is a number of the form is 2n * n + 1 where n is an integer. The first few Cullen numbers are 1, 3, 9, 25, 65, 161, 385, 897, 2049, 4609 . . . . . .
Input : n = 4 Output :65 Input : n = 0 Output : 1 Input : n = 6 Output : 161
Below is implementation of formula. We use bitwise left-shift operator to find 2n, then multiply the result with n and finally returns (1 << n)*n + 1.
Properties of Cullen Numbers:
- Most of the Cullen Numbers are composite numbers.
- n’th Cullen number is divisible by p = 2n – 1 if p is a prime number of the form 8k – 3.
This article is contributed by DANISH_RAZA. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
Attention reader! Don’t stop learning now. Get hold of all the important mathematical concepts for competitive programming with the Essential Maths for CP Course at a student-friendly price. To complete your preparation from learning a language to DS Algo and many more, please refer Complete Interview Preparation Course.