Strobogrammatic number Strobogrammatic number A strobogrammatic number is a number whose numeral is rotationally symmetric, so that it appears the same when rotated 180 degrees. In other words, the numeral looks the same right-side up and upside down (e.g., 69, 96, 1001). A strobogrammatic prime is a strobogrammatic number that is also a prime number, i.e., a number that is only divisible by one and itself (e.g., 11). It is a type of ambigram, words and numbers that retain their meaning when viewed from a different perspective, such as palindromes. When written using standard characters (ASCII), the numbers, 0, 1, 8 are
Infinity calculations by dividing the region into infinitesimal strips of width on the order of formula_2 But in "Arithmetica infinitorum" (1655 also) he indicates infinite series, infinite products and infinite continued fractions by writing down a few terms or factors and then appending "&c." For example, "1, 6, 12, 18, 24, &c." In 1699 Isaac Newton wrote about equations with an infinite number of terms in his work "De analysi per aequationes numero terminorum infinitas". Hermann Weyl opened a mathematico-philosophic address given in 1930 with: The infinity symbol formula_1 (sometimes called the lemniscate) is a mathematical symbol representing the concept of