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SimplesOfVanishingSecondExtensionWithRegularModule on DyckPath ​

The simple modules with no second extension by the regular module.

On DyckPath

FindStat's St001211.

Called as CombinatorialStat(x, "SimplesOfVanishingSecondExtensionWithRegularModule"). The head's page has its examples.

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FindStat St001211

The number of simple modules in the corresponding Nakayama algebra that have vanishing second Ext-group with the regular module.

ObjectValue
[1,0]2
[1,0,1,0]2
[1,1,0,0]3
[1,0,1,0,1,0]3
[1,0,1,1,0,0]3
[1,1,0,0,1,0]3
[1,1,0,1,0,0]3
[1,1,1,0,0,0]4

Data from FindStat, the combinatorial statistic finder; the page at findstat.org/St001211 has the rest.