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
Vanish at infinity Vanish at infinity In mathematics, a function on a normed vector space is said to vanish at infinity if For example, the function defined on the real line vanishes at infinity. More generally, a function formula_4 on a locally compact space (which may not have a norm) vanishes at infinity if, given any positive number formula_5, there is a compact subset formula_6 such that whenever the point formula_8 lies outside of formula_6. In other words, for each positive number formula_5 the set formula_11 is compact. For a given locally compact space formula_12, the set of such functions (where formula_14 is