[Merged by Bors] - feat(NumberTheory/Divisors): add divisorAntidiagonal equivalence.

[CBirkbeck]

---

[github-actions]

PR summary fff1550ff0

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.NumberTheory.TsumDivsorsAntidiagonal (new file)	719

---

Declarations diff

+ divisorsAntidiagonalFactors
+ divisorsAntidiagonalFactors_eq
+ divisorsAntidiagonalFactors_one
+ sigmaAntidiagonalEquivProd
+ sigmaAntidiagonalEquivProd_symm_apply_fst
+ sigmaAntidiagonalEquivProd_symm_apply_snd

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[tb65536]

maintainer delegate

[github-actions]

🚀 Pull request has been placed on the maintainer queue by tb65536.

[riccardobrasca]

Can you add a (very) basic API?

[CBirkbeck]

Sure I've added some basic stuff for now. But if you see anything else I should add let me know.

[CBirkbeck]

Ok I moved this into a new file and you can see where this is going to be used in #28690

[riccardobrasca]

Thanks!

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

• CI Success