"Growth in a Time of Debt." Reinhart, Carmen M., and Kenneth S. Rogoff. American economic review 100.2 (2010): 573-578.

A short article in economics, it now has nearly 5500 citations and is notable enough for its own wikipedia page. The article examines the association between national debt and growth of GDP across several countries, and its most important conclusion is that

When gross external debt reaches 60 percent of GDP, annual growth declines by about two percent; for levels of external debt in excess of 90 percent of GDP, growth rates are roughly cut in half.

When restricted to post-WWII economies, their figure 2 claims even further that GDP growth becomes negative on average if debt exceeds 90%. The result was taken seriously by many economists and politicians and was directly referenced by conservative economic policies in the USA, UK, and EU. They used the Reinhart and Rogoff claim to support spending cuts so that the "deadly" 90% debt ratio could be avoided.

In "Does high public debt consistently stifle economic growth? A critique of Reinhart and Rogoff." Herndon, Thomas, Michael Ash, and Robert Pollin. Cambridge journal of economics 38.2 (2014): 257-279, it was shown that the Reinhart-Rogoff paper overestimated the growth dependence on debt ratio by a 2.5x factor and despite its short length contained numerous statistical errors. The "dumbest" of these was that when constructing the figures for their main result, the authors had misclicked and inadvertently failed to select a large percentage of the countries and years in their excel spreadsheet. The spreadsheet had not been included in the initial publication but was provided to the researchers by special request.

There's subjectivity regarding whether economics is considered a part of the "mathematics research community", but it's inarguable that a 6-page article which dramatically affected economic policy of multiple world powers over the course of three years due to a Microsoft Excel misclick is exceedingly dumb.