MATHS

2008-09-21 5:15 am
1729 係最細既integer有兩種 兩個cube 既 總和
9cube + 10cube = 1729
1 + 12cube = 1729

找下一個好似咁既 integer


The smallest positive integer that can be written as a sum of two positive cubes in two different ways is 1729. Find the next smallest such integer

回答 (1)

2008-09-21 5:42 pm
✔ 最佳答案
Numbers which represent the sum of two cubes in two different ways are call taxicab numbers, from a historical conversation between the mathematicians G.H. Hardy and Srinivasa Ramanujan. (see, for example: http://pi.lacim.uqam.ca/eng/problem_en.html)

A taxicab function of order n represents the smallest number which can be can be represented by the sum of two cubes in n different ways.
For example, Taxicab(2) = 1729.

What your question asks is the next (higher) number that has the same properties as Taxicab(2).

Here are the first 30 numbers that have the properties of Taxicab(2), i.e. each number can be represented by the sum of two cubes in two different ways.
The numbers tobe cubed are shown in parentheses.

Taxicab(2)[1]=1729=(12,1),(10,9)
Taxicab(2)[2]=4104=(16,2),(15,9)
Taxicab(2)[3]=13832=(24,2),(20,18)
Taxicab(2)[4]=20683=(27,10),(24,19)
Taxicab(2)[5]=32832=(32,4),(30,18)
Taxicab(2)[6]=39312=(34,2),(33,15)
Taxicab(2)[7]=40033=(34,9),(33,16)
Taxicab(2)[8]=46683=(36,3),(30,27)
Taxicab(2)[9]=64232=(39,17),(36,26)
Taxicab(2)[10]=65728=(40,12),(33,31)
Taxicab(2)[11]=110656=(48,4),(40,36)
Taxicab(2)[12]=110808=(48,6),(45,27)
Taxicab(2)[13]=134379=(51,12),(43,38)
Taxicab(2)[14]=149389=(53,8),(50,29)
Taxicab(2)[15]=165464=(54,20),(48,38)
Taxicab(2)[16]=171288=(55,17),(54,24)
Taxicab(2)[17]=195841=(58,9),(57,22)
Taxicab(2)[18]=216027=(60,3),(59,22)
Taxicab(2)[19]=216125=(60,5),(50,45)
Taxicab(2)[20]=262656=(64,8),(60,36)
Taxicab(2)[21]=327763=(67,30),(58,51)
Taxicab(2)[22]=314496=(68,4),(66,30)
Taxicab(2)[23]=320264=(68,18),(66,32)
Taxicab(2)[24]=402597=(69,42),(61,56)
Taxicab(2)[25]=373464=(72,6),(60,54)
Taxicab(2)[26]=439101=(76,5),(69,48)
Taxicab(2)[27]=443889=(76,17),(73,38)
Taxicab(2)[28]=513856=(78,34),(72,52)
Taxicab(2)[29]=513000=(80,10),(75,45)
Taxicab(2)[30]=515375=(80,15),(71,54)


收錄日期: 2021-04-13 16:05:27
原文連結 [永久失效]:
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