Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/MathTrig.php
public static function SUMSQ(...$args)
    {
        $returnValue = 0;

        // Loop through arguments
        foreach (Functions::flattenArray($args) as $arg) {
            // Is it a numeric value?
            if ((is_numeric($arg)) && (!is_string($arg))) {
                $returnValue += ($arg * $arg);
            }
        }

        return $returnValue;
    }
public static function SUMSQ(...$args)
    {
        $returnValue = 0;

        // Loop through arguments
        foreach (Functions::flattenArray($args) as $arg) {
            // Is it a numeric value?
            if ((is_numeric($arg)) && (!is_string($arg))) {
                $returnValue += ($arg * $arg);
            }
        }

        return $returnValue;
    }
SUMSQ.

SUMSQ returns the sum of the squares of the arguments

Excel Function:
SUMSQ(value1[,value2[, ...]])

@category Mathematical and Trigonometric Functions

@param mixed ...$args Data values

@return float