204 (number)

Source: Wikipedia, the free encyclopedia.
← 203 204 205 →
Cardinaltwo hundred four
Ordinal204th
(two hundred fourth)
Factorization22 × 3 × 17
Divisors1, 2, 3, 4, 6, 12, 17, 34, 51, 68, 102, 204
Greek numeralΣΔ´
Roman numeralCCIV
Binary110011002
Ternary211203
Senary5406
Octal3148
Duodecimal15012
HexadecimalCC16

204 (two hundred [and] four) is the natural number following 203 and preceding 205.

In mathematics

204 is a refactorable number.[1] 204 is a square pyramidal number: 204 balls may be stacked in a pyramid whose base is an 8 × 8 square.[2] Its square, 2042 = 41616, is the fourth square triangular number.[3] As a figurate number, 204 is also a nonagonal number[4] and a truncated triangular pyramid number.[5] 204 is a member of the Mian-Chowla sequence.[6]

There are exactly 204

chess queens on a 5 × 5 board,[8] exactly 204 squares of an infinite chess move that are eight knight's moves from the center,[9] exactly 204 strings of length 11 over a three-letter alphabet with no consecutively-repeated substring,[10] and exactly 204 ways of immersing an oriented circle into the oriented plane so that it has four double points.[11]

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.[12]

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

References

  1. ^ Sloane, N. J. A. (ed.). "Sequence A033950 (Refactorable numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-04-18.
  2. ^ Sloane, N. J. A. (ed.). "Sequence A000330 (Square pyramidal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  3. ^ Sloane, N. J. A. (ed.). "Sequence A001109 (a(n)^2 is a triangular number)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  4. ^ Sloane, N. J. A. (ed.). "Sequence A001106 (9-gonal (or enneagonal or nonagonal) numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  5. ^ Sloane, N. J. A. (ed.). "Sequence A051937 (Truncated triangular pyramid numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  6. ^ Sloane, N. J. A. (ed.). "Sequence A005282 (Mian-Chowla Sequence)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-04-19.
  7. ^ Sloane, N. J. A. (ed.). "Sequence A027377 (Number of irreducible polynomials of degree n over GF(4); dimensions of free Lie algebras)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  8. ^ Sloane, N. J. A. (ed.). "Sequence A047659 (Number of ways to place 3 nonattacking queens on an n X n board)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  9. ^ Sloane, N. J. A. (ed.). "Sequence A018842 (Number of squares on infinite chess-board at n knight's moves from center)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  10. ^ Sloane, N. J. A. (ed.). "Sequence A006156 (Number of ternary squarefree words of length n)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  11. ^ Sloane, N. J. A. (ed.). "Sequence A008980 (Number of immersions of the oriented circle into the oriented plane with n double points)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation..
  12. ^ Sloane, N. J. A. (ed.). "Sequence A213784 (Numbers n such both n and n^2 are sums of a twin prime pair)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  13. ^ Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, itef.org, retrieved 2014-07-29.
  14. ^ Sloane, N. J. A. (ed.). "Sequence A057804 (Number of ways of getting at least ... in wild-card poker with 1 joker)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. See also OEISA057807.