Plenty of people want to work at Mountain View-based Google — a company that takes great pride in an employee-friendly culture that offers free meals and lucrative stock options.

But Google remains picky about whom it hires, even as its payroll has ballooned from just fewer than 700 employees at the end of 2002 to about 2,700 workers today.

In its quest to identify the programming elite, Google recently inserted an unusual aptitude test in such magazines as MIT's Technology Review, the Linux Journal, Mensa, Dr. Dobbs and Physics Today.

The 21-question test includes such geek brain twisters like, "How many different ways can you color an icosahedron with one of three colors on each face?" and "On an infinite, two-dimensional rectangular lattice of 1-ohm resistors, what is the resistance between two nodes that are a knight's move away?"

The test also includes more subjective, tongue-in-cheek requests like "Write a haiku describing possible methods for predicting search traffic seasonality" and "What is the most beautiful math equation ever derived?"

Google has received an enthusiastic response to the test, said Alan Eustace, the company's vice president of engineering research and systems, though many of the people sending in their answers are economists, professors and other intellectuals more interested in a mental challenge than a job.

During the past two years, Google has offered cash prizes to computer engineers who compete against each other to solve complex coding problems.

The programming battles are becoming an increasingly popular way to recruit skilled programmers away from a number of high-tech companies, including two of Google's biggest rivals, Yahoo Inc. and Microsoft Corp.

The companies stage the events in conjunction with Glastonbury, Conn.-based TopCoder, which has developed an automated system for scoring the competitions.

TopCoder, formed in 1991, now boasts 43,000 members who enter the competitions looking for extra cash, bragging rights and a little more cachet on their résumés, said TopCoder President Rob Hughes.

"These are people who generally aren't into self-promotion and feel a little intimidated going to formal job interviews," Hughes said.

Google's latest competition, completed earlier this month, attracted 7,500 entrants — a field whittled down to 50 finalists through a series of elimination rounds.

"When you can get together 50 of the most talented computer scientists in the world, there's a chance that you are going to hire some of them," Eustace said.

The company gave a total of $50,000 to the finalists, who also received an all expenses-paid trip to Google's headquarters.