The Diophantine Equation 2y2 − x2 = z2 (Part I/IIA)

A Method for Generating Random Access Equations

Picture of a square

Generation of Tables of Equations

Math and computer methods in Part I and Part II were used to solve the Diophantine equation 2y2 − x2 = z2 for various triple values of (a1,b1,c1) but performed in a sequential manner. However, these methods require longer and longer calculation times if the desired triple, (a,b,c), is composed of extremely large numbers.

The method in this section uses the triples (a1,b1,c1) from column 2, 3 and 4 of Part I and Part II slightly modified to produce Tables I and II here, while Tables III thru VIII of triples were generated using the same computer program as in Parts I and II but not published online. The method is identical to those of the just published online papers Part III and Part IV where the purpose was to generate equations from the data to provide a method of obtaining new triples via random access. The method, repeated here, starts by setting up the table headings with three equations, constructed from the tabulated data, and placed beneath their appropriate a, b and c variables.

The table headings contain the equations generated from the data for each of the (a1,b1,-c1) and (a1,-b1, c1) triples, shown in the captions for all the tables below, and are generally of the form:

a1,b1,-c1
δ1a b c δ2
k 7k2 - 3mk + n 5k2 - 2mk + n k2 + mk - n
a1,-b1,c1
δ1a b c δ2
k 7k2 + 2mk - 2n 5k2 + mk + 2n k2 - 4mk - 2n

where k is a counter starting at zero, D is the coefficient of y and (n, m) are values taken from the table below so that whenever n = j2 then m = 2j for all j > 0:

Table of n & m values
n149162536496481100...
m2468101214161820...

Since there are an infinite number of (n, m) integers there are also an infinite number of tables which can be tabulated with their accompanying equations; equations whose purpose is to generate the triples either by random or sequential access. In addition, a substantial number of triples are composed of numbers which can be simplified further via prime division.

The utility of these equations is that they are useful for generating the triples via a random access of k unlike Parts I and II which are sequential methods for generating triples. However, in order to generate these new equations we need to use the sequential method to generate a small number of triples which are then used to generate the requisite new equations, the reason for the tables below. The caption for each table pertains to the initial triple value (a1,b1,c1) used in the computer program calculation. Note that the δ1δ1 and δ2δ2 are 14 and 2, respectively, for all the tables. In addition, a substantial number of triples are composed of numbers which can be simplified further via prime division.

Table I (1,1,-1)
δ1a b c δ2
k 7k2 - 12k + 4 5k2 - 8k + 4 k2 + 4k - 4
044-4
-55
1-111
97
2888
239
3312517
3711
4685228
5113
51198941
6515
618413656
7917
726319373
Table II (1,-1,1)
δ1a b c δ2
k 7k2 + 8k - 8 5k2 + 4k + 8 k2 - 16k - 8
0-88-8
15-15
1717-23
29-13
23636-36
43-11
37965-47
57-9
4136104-56
71-7
5207153-63
85-5
6292212-68
99-3
7391281-71

Next comes Tables III and IV.

Table III (1,1,-2)
δ1a b c δ2
k 7k2 - 18k + 9 5k2 - 12k + 9 k2 + 6k - 9
099-9
-117
1-22-2
39
2157
1711
3181818
3113
4494131
4515
5947446
5917
615311763
7319
722617082
Table IV (1,-2,1)
δ1a b c δ2
k 7k2 + 12k - 18 5k2 + 6k + 18 k2 - 24k - 18
0-1818-18
19-23
1129-41
33-21
23450-62
47-19
38181-81
61-17
4142122-98
75-15
5217173-113
89-13
6306234-126
103-11
7409305-137

Next comes Tables V and VI.

Table V (1,1,-3)
δ1a b c δ2
k 7k2 - 24k + 16 5k2 - 16k + 16 k2 + 8k - 16
01616-16
-179
1-15-7
-311
2-444
1113
371317
2515
4323232
3917
5716149
5319
612410068
6721
719114989
Table VI (1,-3,1)
δ1a b c δ2
k 7k2 + 16k - 32 5k2 + 8k + 32 k2 - 32k - 32
0-3232-32
23-31
1-945-63
39-29
22868-92
51-27
379101-119
65-25
4144144-144
79-23
5223197-167
93-21
6316260-188
107-19
7423333-207

Finally we have Tables VII and VIII.

Table VII (1,1,-4)
δ1a b c δ2
k 7k2 - 30k + 25 5k2 - 20k + 25 k2 + 10k - 25
025-25-25
-2311
1210-14
-913
2-75-1
515
3-21014
1917
4172531
3319
5505050
4721
6978571
6123
715813094
Table VIII (1,-4,1)
δ1a b c δ2
k 7k2 + 20k - 50 5k2 + 10k + 50 k2 - 40k - 50
0-5050-50
27-39
1-2365-89
41-37
21890-126
55-35
373125-161
69-33
4142170-194
83-31
5225225225
97-29
6322290-254
111-27
7433365-281

Only eight triples, (a1,b1,c1), were used in the calculation for the Diophantine equation 2y2 − x2 = z2 to get an idea of its versatility. Note that the tables produced can be expanded downward indefinitely. In addition, using the tables one can generate the appropriate equations that are useful for generating any triple in a table using a random access method which obviates the need to go through a sequential time consuming process.

This concludes Part I/II. Go back to Part I or Part II.

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Copyright © 2020 by Eddie N Gutierrez. E-Mail: enaguti1949@gmail.com