| 词条 | 229 (number) |
| 释义 |
| number = 229 | prime = yes }} 229 (two hundred [and] twenty-nine) is the natural number following 228 and preceding 230. It is a prime number, and a regular prime.[1] It is also a full reptend prime, meaning that the decimal expansion of the unit fraction 1/229 repeats periodically with as long a period as possible.[2] With 227 it is the larger of a pair of twin primes,[3] and it is also the start of a sequence of three consecutive squarefree numbers.[4] It is the smallest prime that, when added to the reverse of its decimal representation, yields another prime: 229 + 922 = 1151.[5] There are 229 cyclic permutations of the numbers from 1 to 7 in which none of the numbers is mapped to its successor (mod 7),[6] 229 rooted tree structures formed from nine carbon atoms,[7] and 229 triangulations of a polygon formed by adding three vertices to each side of a triangle.[8] There are also 229 different projective configurations of type (123123), in which twelve points and twelve lines meet with three lines through each of the points and three points on each of the lines,[9] all of which may be realized by straight lines in the Euclidean plane.[10][11] The complete graph K13 has 229 crossings in its straight-line drawing with the fewest possible crossings.[12][13] References1. ^{{Cite OEIS|sequencenumber=A007703|name=Regular primes}} 2. ^{{Cite OEIS|sequencenumber=A001913|name=Full reptend primes: primes with primitive root 10}} 3. ^{{Cite OEIS|sequencenumber=A006512|name=Greater of twin primes}} 4. ^{{Cite OEIS|sequencenumber=A007675|name=Numbers n such that n, n+1 and n+2 are squarefree}} 5. ^{{Cite OEIS|sequencenumber=A061783|name=Primes p such that p + (p reversed) is also a prime}} 6. ^{{Cite OEIS|sequencenumber=A000757|name=Number of cyclic permutations of [n] with no i->i+1 (mod n)}} 7. ^{{Cite OEIS|sequencenumber=A000678|name=Number of carbon (rooted) trees with n carbon atoms = unordered 4-tuples of ternary trees}} 8. ^{{Cite OEIS|sequencenumber=A087809|name=Number of triangulations (by Euclidean triangles) having 3+3n vertices of a triangle with each side subdivided by n additional points}} 9. ^{{Cite OEIS|sequencenumber=A001403|name=Number of combinatorial configurations of type (n_3)}} 10. ^{{Cite OEIS|sequencenumber=A099999|name=Number of geometrical configurations of type (n_3)}} 11. ^{{citation | last = Gropp | first = Harald | doi = 10.1016/S0012-365X(96)00327-5 | issue = 1–3 | journal = Discrete Mathematics | pages = 137–151 | title = Configurations and their realization | volume = 174 | year = 1997}}. 12. ^{{Cite OEIS|sequencenumber=A014540|name=Rectilinear crossing number of complete graph on n nodes}} 13. ^{{citation | last1 = Aichholzer | first1 = Oswin | last2 = Krasser | first2 = Hannes | doi = 10.1016/j.comgeo.2005.07.005 | issue = 1 | journal = Computational Geometry | mr = 2264046 | pages = 2–15 | title = Abstract order type extension and new results on the rectilinear crossing number | volume = 36 | year = 2007}}. See also
1 : Integers |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。