Using a tabu search algorithm I managed to improve 36 lower bounds
on numbers of nonisomorphic block designs (BIBDs) given in the
CRC Handbook of
Combinatorial Designs (table 1.28). Here are the new lower bounds
and incidence matrices of the constructed
designs (gnu-zipped):
| No. | (v,k,l) | CRC | New | No. | (v,k,l) | CRC | New | |
| 69 | (19,4,2) | 423 | 10000 | 361 | (19,4,4) | 424 | 5000 | |
| 70 | (13,4,3) | 3702 | 10000 | 416 | (11,5,10) | 3337 | 10000 | |
| 102 | (15,5,4) | 207 | 10000 | 447 | (14,4,6) | 4 | 2500 | |
| 123 | (16,5,4) | 11 | 10000 | 520 | (29,4,3) | 1 | 200 | |
| 124 | (13,5,5) | 30 | 10000 | 525 | (15,5,8) | 104 | 10000 | |
| 128 | (16,6,5) | 15 | 300 | 529 | (15,6,10) | 118 | 10000 | |
| 147 | (25,4,2) | 17 | 1000 | 606 | (16,5,8) | 12 | 5000 | |
| 148 | (17,4,3) | 1 | 10000 | 607 | (13,5,10) | 31 | 10000 | |
| 149 | (13,4,4) | 2462 | 10000 | 688 | (17,4,6) | 1 | 250 | |
| 220 | (20,4,3) | 1 | 2500 | 742 | (16,6,11) | 1 | 10000 | |
| 221 | (20,5,4) | 1 | 400 | 785 | (18,4,6) | 1 | 100 | |
| 238 | (31,4,2) | 1 | 50 | 788 | (18,6,10) | 4 | 1000 | |
| 239 | (21,4,3) | 1 | 2500 | 825 | (15,5,10) | 1 | 1000 | |
| 242 | (11,4,6) | 1 | 10000 | 835 | (16,7,14) | 1 | 1000 | |
| 246 | (17,5,5) | 1 | 5000 | 1000 | (20,5,8) | 1 | 1000 | |
| 247 | (11,5,8) | 4394 | 10000 | 1036 | (16,6,13) | 1 | 1000 | |
| 284 | (16,6,7) | 1 | 5000 | 1037 | (14,6,15) | 1 | 5000 | |
| 340 | (24,4,3) | 1 | 1000 | 1094 | (17,5,10) | 1 | 1000 | |
The program used to find the designs is also available for download.
Vedran Krcadinac, 14.1.2002.