Use (as first grid) the 5x5 carpet of the 3x3 magic square and (as second grid) the 3x3 carpet of the 5x5 magic square to construct a 15x15 magic square. Take [number -/- 1] x 25 from the first grid and add 1x number from the same cell of the second grid.
25 x [number -/- 1] from 5x5 carpet of a 3x3 magic square
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
2 |
9 |
4 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
7 |
5 |
3 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
6 |
1 |
8 |
+ 1x number from 3x3 carpet of a 5x5 (pan)magic square
1 |
19 |
7 |
25 |
13 |
1 |
19 |
7 |
25 |
13 |
1 |
19 |
7 |
25 |
13 |
10 |
23 |
11 |
4 |
17 |
10 |
23 |
11 |
4 |
17 |
10 |
23 |
11 |
4 |
17 |
14 |
2 |
20 |
8 |
21 |
14 |
2 |
20 |
8 |
21 |
14 |
2 |
20 |
8 |
21 |
18 |
6 |
24 |
12 |
5 |
18 |
6 |
24 |
12 |
5 |
18 |
6 |
24 |
12 |
5 |
22 |
15 |
3 |
16 |
9 |
22 |
15 |
3 |
16 |
9 |
22 |
15 |
3 |
16 |
9 |
1 |
19 |
7 |
25 |
13 |
1 |
19 |
7 |
25 |
13 |
1 |
19 |
7 |
25 |
13 |
10 |
23 |
11 |
4 |
17 |
10 |
23 |
11 |
4 |
17 |
10 |
23 |
11 |
4 |
17 |
14 |
2 |
20 |
8 |
21 |
14 |
2 |
20 |
8 |
21 |
14 |
2 |
20 |
8 |
21 |
18 |
6 |
24 |
12 |
5 |
18 |
6 |
24 |
12 |
5 |
18 |
6 |
24 |
12 |
5 |
22 |
15 |
3 |
16 |
9 |
22 |
15 |
3 |
16 |
9 |
22 |
15 |
3 |
16 |
9 |
1 |
19 |
7 |
25 |
13 |
1 |
19 |
7 |
25 |
13 |
1 |
19 |
7 |
25 |
13 |
10 |
23 |
11 |
4 |
17 |
10 |
23 |
11 |
4 |
17 |
10 |
23 |
11 |
4 |
17 |
14 |
2 |
20 |
8 |
21 |
14 |
2 |
20 |
8 |
21 |
14 |
2 |
20 |
8 |
21 |
18 |
6 |
24 |
12 |
5 |
18 |
6 |
24 |
12 |
5 |
18 |
6 |
24 |
12 |
5 |
22 |
15 |
3 |
16 |
9 |
22 |
15 |
3 |
16 |
9 |
22 |
15 |
3 |
16 |
9 |
= 15x15 magic square
26 |
219 |
82 |
50 |
213 |
76 |
44 |
207 |
100 |
38 |
201 |
94 |
32 |
225 |
88 |
160 |
123 |
61 |
154 |
117 |
60 |
173 |
111 |
54 |
167 |
110 |
73 |
161 |
104 |
67 |
139 |
2 |
195 |
133 |
21 |
189 |
127 |
20 |
183 |
146 |
14 |
177 |
145 |
8 |
196 |
43 |
206 |
99 |
37 |
205 |
93 |
31 |
224 |
87 |
30 |
218 |
81 |
49 |
212 |
80 |
172 |
115 |
53 |
166 |
109 |
72 |
165 |
103 |
66 |
159 |
122 |
65 |
153 |
116 |
59 |
126 |
19 |
182 |
150 |
13 |
176 |
144 |
7 |
200 |
138 |
1 |
194 |
132 |
25 |
188 |
35 |
223 |
86 |
29 |
217 |
85 |
48 |
211 |
79 |
42 |
210 |
98 |
36 |
204 |
92 |
164 |
102 |
70 |
158 |
121 |
64 |
152 |
120 |
58 |
171 |
114 |
52 |
170 |
108 |
71 |
143 |
6 |
199 |
137 |
5 |
193 |
131 |
24 |
187 |
130 |
18 |
181 |
149 |
12 |
180 |
47 |
215 |
78 |
41 |
209 |
97 |
40 |
203 |
91 |
34 |
222 |
90 |
28 |
216 |
84 |
151 |
119 |
57 |
175 |
113 |
51 |
169 |
107 |
75 |
163 |
101 |
69 |
157 |
125 |
63 |
135 |
23 |
186 |
129 |
17 |
185 |
148 |
11 |
179 |
142 |
10 |
198 |
136 |
4 |
192 |
39 |
202 |
95 |
33 |
221 |
89 |
27 |
220 |
83 |
46 |
214 |
77 |
45 |
208 |
96 |
168 |
106 |
74 |
162 |
105 |
68 |
156 |
124 |
62 |
155 |
118 |
56 |
174 |
112 |
55 |
147 |
15 |
178 |
141 |
9 |
197 |
140 |
3 |
191 |
134 |
22 |
190 |
128 |
16 |
184 |
Each random chosen 3x5 or 5x3 rectangle gives the magic sum of 1695.
I have used the method composite, AxB compact to construct
12x12, 15x15, 20x20, 21x21, 24x24, 28x28, 30x30a and 30x30b