In math, what lists can be summed into series?

More Questions:

In "The Twelve Days of Christmas', what did my true love send to me on the fifth day?

How many players are there on a soccer team?

What woman's rise to fame is the subject of the 1997 book "Just Desserts"?

What city's orchestra did Eugene Ormandy conduct for forty-four years?

In Greek mythology who was the son of Hypnos, who is considered god of dreams?

What does the Kardashev scale measure?

What mission was the first successful manned mission to land on the Moon?

What TV series, which ran from 2004 thru 2008, was a spin-off from "The Practice"?

Who played the role of TV's B. J. Poteet?

Who has been played in a movie by both John Gavin and Rex Harrison?

What is the name of the theme song from the TV show "Friends"?

The 2002 US film "The Ring" is based on a 1990's film produced and released in what other country?

Who played weatherman Phil Connors in the movie "Groundhog Day"?

How many of Henry VIII's wives were executed?

What virtual reality set was launched in March, 2016?