Founded just five months ago, Equals, a start-up pitching itself as the third-generation spreadsheet, has already raised $22.6 million.  The San Francisco-based company, which is aiming to take on the behemoths that are Excel and Google Sheets, raised a $6.6 million seed round in July of this year and has now just closed a $16 million Series A round led by Andreessen Horowitz, with participation from Craft Ventures, Box Group, Worklife and Combine. Tristan Handy, chief executive of DBT, a data transformation tool, and April Underwood, former chief product officer at Slack, are also investing.   The start-up was co-founded by…