Table of possible values for ring construction of OBIBDs

This is for the ring of integers Zv, where v is a not a power of a prime. The final column gives i values of m for up to s sets of treatments. There are other solutions for k = 2. To get a solution, the first initial block for the first set of treatments is given by the column headed block; the first initial block for a second or further sets of treatments is given by multiplying the elements of the block by the multiplier. The other initial blocks are given by multiplying these two blocks by coset representatives (for the first block) in the multiplicative group of the ring. Finally, develop these initial blocks additively.

v k Block Multiplier(s)
65 2 (1,64) 8
85 2 (1,84) 13
91 2 (1,90) 9,10
133 2 (1,132) 11,12
145 2 (1,144) 12
185 2 (1,184) 43
205 2 (1,204) 32
217 2 (1,216) 25,26
221 2 (1,220) 21
247 2 (1,246) 68,69
259 2 (1,258) 100,101
265 2 (1,264) 23
301 2 (1,300) 79,80
305 2 (1,304) 72
325 2 (1,324) 18
341 2 (1,340) 29,47,159,163
365 2 (1,364) 27
377 2 (1,376) 70
403 2 (1,402) 87,88
425 2 (1,424) 132
427 2 (1,426) 74,75
445 2 (1,444) 123
451 2 (1,450) 59,107,127,174
469 2 (1,468) 37,38
481 2 (1,480) 31,162,193,269,270
493 2 (1,492) 157
91 3 (1,9,81) 10
91 3 (1,16,74) 17
133 3 (1,11,121) 12
133 3 (1,30,102) 31
217 3 (1,37,431) 38
217 3 (1,163,305) 164
247 3 (1, 68, 178) 69
247 3 (1, 87, 159) 88
259 3 (1, 100, 158) 101
259 3 (1, 121, 137) 122
301 3 (1, 79, 221) 80
301 3 (1, 135, 165) 136
403 3 (1, 87, 315) 88
403 3 (1, 191, 211) 192
427 3 (1, 74, 352) 75
427 3 (1, 135, 291) 136
469 3 (1, 37, 431) 38
469 3 (1, 163, 305) 164
481 3 (1, 100, 380) 45,101,216
481 3 (1, 211, 269) 31,193,212
481 4 (1,31,450,480) 211,162
481 4 (1, 216, 480, 265) 97,119
341 5 (1, 4, 16, 64, 256) 85
341 5 (1, 47, 159, 163, 312) 29
341 5 (1, 70, 126, 190, 295) 46
341 5 (1, 97, 157, 202, 225) 116
451 5 (1, 16, 37, 141, 256) 195
451 5 (1, 201, 92, 262, 346) 105
451 5 (1, 119, 180, 223, 379) 72
451 5 (1, 59, 174, 324, 344) 107
481 6 (1, 100, 101, 381, 380, 480) 45

The solution given by Furino for k = 3 was for numbers of the form r2+r+1, where r = 0,2 mod 3, The fundamental subgroup was of form {1,r,r2}. Only two of the solutions given above are of this form (v = 91, 133). All of them can be solved as Galois Rings, as can all the solutions for other k. There also values of v for which there is no solution here, but for which a Galois Ring solution would exist e.g. for k = 2, 45 and other multiples of 9.

The solutions for k = 2 are all equivalent to SAMDRRs or SOLS. There are therefore, for example, 5 mutually orthogonal SOLS for 481. In all cases, the first block is of the form (1,-1). I assume this has been done elsewhere at some time.