SQL Server 2019

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CREATE TABLE [dbo].[Asset]
(
    [AssetSeqNumber] [bigint] NULL,
    [AssetType] [varchar](100) NULL
);

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (1, N'Tree')

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (2, N'Tree')

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (3, N'Tree')

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (4, N'Barbecue')

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (5, N'Bridge')

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (101, N'Tree')

INSERT [dbo].[Asset] ([AssetSeqNumber], [AssetType]) 
VALUES (102, N'Tree')
7 rows affected

SELECT
    AssetType, 
    COUNT(AssetSeqNumber) AS count,
    STUFF((SELECT DISTINCT ',' + CAST(AssetSeqNumber AS varchar(100))
           FROM Asset
           WHERE AssetType = a.AssetType AND AssetSeqNumber IN (1, 2, 3, 4, 5)
           FOR XML PATH ('')), 1, 1, '') AS AssetIds
FROM 
    Asset AS a
WHERE
    a.AssetSeqNumber IN (1, 2, 3, 4, 5)
GROUP BY 
    AssetType


AssetType
count
AssetIds


Barbecue
1
4

Bridge
1
5

Tree
3
1,2,3


SELECT AssetType, 
       COUNT(*) [Count],
       STRING_AGG(AssetSeqNumber, ',') AssetIds
FROM Asset
WHERE AssetSeqNumber IN (1, 2, 3, 4, 5)
GROUP BY AssetType 


AssetType
Count
AssetIds


Barbecue
1
4

Bridge
1
5

Tree
3
1,2,3