What is pi, and how did it originate? Succinctly, pi--which is written as the Greek letter for p, or --is the ratio of the circumference of any circle to the diameter of that circle. Regardless of the circle's size, this ratio will always equal pi. In decimal form, the value of pi is approximately 3.14.
Inverted repeat. An inverted repeat (or IR) is a single stranded sequence of nucleotides followed downstream by its reverse complement. The intervening sequence of nucleotides between the initial sequence and the reverse complement can be any length including zero. When the intervening length is zero, the composite sequence is a palindromic sequence.
The Worldâs Longest Palindromes. Retired Article â¢ written by Daniel Lew. A palindrome is a word, phrase, verse or sentence that reads the same backward or forward. In 2002, Peter Norvig read that Dan Hoey had created a computer program that had generated a 540 word palindrome in 1984. Thinking he could do one better, Norvig created his own version of the program.