If your columns are really numbered (column56, column57, ...) you can use dynamic sql here.

declare @I int = 56;
declare @sql nvarchar(1000);
while @I <= 79
begin
    set @sql = N'alter table dbo.MyTable drop column ' + 
                '[column' + cast(@I as nvarchar(30)) + N']';
    exec sp_executesql @sql;
    set @I += 1;
end;

You can also delete columns using the table designer in Sql Server Management Studio ( see delete-columns-from-a-table )

Try generating the necessary ALTER TABLE statements dynamically from column56 to column79:

DECLARE @TableName NVARCHAR(128) = 'table_name'
DECLARE @DropColumns NVARCHAR(MAX) = ''

SELECT @DropColumns = @DropColumns + QUOTENAME(name) + ', '
FROM sys.columns
WHERE object_id = OBJECT_ID(@TableName)
    AND column_id >= (SELECT column_id FROM sys.columns WHERE object_id = OBJECT_ID(@TableName) AND name = 'column56')
    AND column_id <= (SELECT column_id FROM sys.columns WHERE object_id = OBJECT_ID(@TableName) AND name = 'column79')

SET @DropColumns = LEFT(@DropColumns, LEN(@DropColumns) - 1) -- Remove the trailing comma

DECLARE @Sql NVARCHAR(MAX) = 'ALTER TABLE ' + QUOTENAME(@TableName) + ' DROP COLUMN ' + @DropColumns
PRINT @Sql -- Optional: Print the generated SQL statement

-- Uncomment the following line to execute the dynamic SQL statement
-- EXEC sp_executesql @Sql