Timeline for Number of finite index subgroups in a free abelian group
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| Aug 4, 2022 at 15:12 | comment | added | Carl-Fredrik Nyberg Brodda | @SamHopkins Thanks for the excellent edits! | |
| Aug 4, 2022 at 14:44 | history | edited | Sam Hopkins | CC BY-SA 4.0 |
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| Aug 4, 2022 at 4:28 | history | edited | Sam Hopkins | CC BY-SA 4.0 |
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| Aug 3, 2022 at 20:56 | comment | added | Sam Hopkins | (By the way, a proof for this recurrence can be obtained, as I suggested in a comment above, using Hermite normal form; this is explained in the slides of Alex Suciu I linked.) | |
| Aug 3, 2022 at 19:19 | vote | accept | Ehud Meir | ||
| Aug 3, 2022 at 18:31 | history | edited | Sam Hopkins | CC BY-SA 4.0 |
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| Aug 3, 2022 at 17:50 | comment | added | Sam Hopkins | Hmm, I guess it is possible both recurrences are correct but that seems weird. Also, I switched your $n$ and $m$ to be more consistent with the notation of the question-asker. EDIT: okay, I see that both recursions give the same thing. | |
| Aug 3, 2022 at 17:49 | history | edited | Sam Hopkins | CC BY-SA 4.0 |
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| Aug 3, 2022 at 17:44 | history | edited | Carl-Fredrik Nyberg Brodda | CC BY-SA 4.0 |
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| Aug 3, 2022 at 17:44 | comment | added | Carl-Fredrik Nyberg Brodda | @SamHopkins Yes, closed formula is bad phrasing! Both formulas are correct (assuming the OEIS page is right). | |
| Aug 3, 2022 at 17:41 | history | edited | Sam Hopkins | CC BY-SA 4.0 |
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| Aug 3, 2022 at 17:39 | comment | added | Sam Hopkins | Well, I would not call this a closed formula - it's a recurrence. | |
| Aug 3, 2022 at 17:36 | history | answered | Carl-Fredrik Nyberg Brodda | CC BY-SA 4.0 |