204 (number)
{{Infobox number
| number = 204
| divisor = 1, 2, 3, 4, 6, 12, 17, 34, 51, 68, 102, 204
}}
204 (two hundred [and] four) is the natural number following 203 and preceding 205.
In mathematics
204 is a refactorable number.{{Cite OEIS|1=A033950|2=Refactorable numbers|access-date=2016-04-18}} 204 is a square pyramidal number: 204 balls may be stacked in a pyramid whose base is an 8 × 8 square.{{Cite OEIS|A000330|name=Square pyramidal numbers}} Its square, 2042 = 41616, is the fourth square triangular number.{{Cite OEIS|A001109|name=a(n)^2 is a triangular number}} As a figurate number, 204 is also a nonagonal number{{Cite OEIS|A001106|name=9-gonal (or enneagonal or nonagonal) numbers}} and a truncated triangular pyramid number.{{Cite OEIS|A051937|name=Truncated triangular pyramid numbers}} 204 is a member of the Mian-Chowla sequence.{{Cite OEIS|1=A005282|2=Mian-Chowla Sequence|access-date=2016-04-19}}
There are exactly 204 irreducible quintic polynomials over a four-element field,{{Cite OEIS|A027377|name=Number of irreducible polynomials of degree n over GF(4); dimensions of free Lie algebras}} exactly 204 ways to place three non-attacking chess queens on a 5 × 5 board,{{Cite OEIS|A047659|name=Number of ways to place 3 nonattacking queens on an n X n board}} exactly 204 squares of an infinite chess move that are eight knight's moves from the center,{{Cite OEIS|A018842|name=Number of squares on infinite chess-board at n knight's moves from center}} exactly 204 strings of length 11 over a three-letter alphabet with no consecutively-repeated substring,{{Cite OEIS|A006156|name=Number of ternary squarefree words of length n}} and exactly 204 ways of immersing an oriented circle into the oriented plane so that it has four double points.{{Cite OEIS|A008980|name=Number of immersions of the oriented circle into the oriented plane with n double points}}.
Both 204 and its square are sums of a pair of twin primes: 204 = 101 + 103 and 2042 = 41616 = 20807 + 20809. The only smaller numbers with the same property are 12 and 84.{{Cite OEIS|A213784|name=Numbers n such both n and n^2 are sums of a twin prime pair}}
204 is a sum of all the perfect squares from 1 to 64 (i.e. 12 + 22 + 32 + 42 + 52 + 62 + 72 + 82 = 204).
In other fields
- 204 is the HTTP status code indicating the request was successfully fulfilled and that there is no additional content to send in the response payload body.[http://tools.ietf.org/html/rfc7231#section-6.3.5 Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content], itef.org, retrieved 2014-07-29.