From that download page you should be able to select the "Quartus II Software (6)" link on the left hand side to get to the legacy software download page.
It should get you here:
https://www.intel.com/content/www/us/en/collections/products/fpga/software/downloads.html?s=Newest&f:guidetmD240C377263B4C70A4EA0E452D0182CA=%5BQuartus%C2%AE%20II%20Software%3BQuartus%C2%AE%20II%20Web%20Edition%5D
which is the QuartusII 13.1 web download links, for either Windows or Linux, your choice.
Follow those and you can download either full ISO images or the parts of the software you require.
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