7 Up up with the formula for a lemon-lime soft drink in 1929. The product, originally named "Bib-Label Lithiated Lemon-Lime Soda", was launched two weeks before the Wall Street Crash of 1929. It contained lithium citrate, a mood-stabilizing drug, until 1948. It was one of a number of patent medicine products popular in the late-19th and early-20th centuries. Its name was later shortened to "7 Up Lithiated Lemon Soda" before being further shortened to just "7 Up" by 1936. A myth exists that the 7 Up name comes from the drink having a pH over 7. That would make it neutral or
Combination can be written using factorials as formula_2 whenever formula_3, and which is zero when formula_4. The set of all "k"-combinations of a set "S" is often denoted by formula_5. Combinations refer to the combination of "n" things taken "k" at a time without repetition. To refer to combinations in which repetition is allowed, the terms "k"-selection, "k"-multiset, or "k"-combination with repetition are often used. If, in the above example, it were possible to have two of any one kind of fruit there would be 3 more 2-selections: one with two apples, one with two oranges, and one with two pears.