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lib/PhpSpreadsheet/Calculation/MathTrig/SeriesSum.php

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+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
+
+use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception;
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+
+class SeriesSum
+{
+    use ArrayEnabled;
+
+    /**
+     * SERIESSUM.
+     *
+     * Returns the sum of a power series
+     *
+     * @param mixed $x Input value
+     * @param mixed $n Initial power
+     * @param mixed $m Step
+     * @param mixed[] $args An array of coefficients for the Data Series
+     *
+     * @return array|float|int|string The result, or a string containing an error
+     */
+    public static function evaluate(mixed $x, mixed $n, mixed $m, ...$args): array|string|float|int
+    {
+        if (is_array($x) || is_array($n) || is_array($m)) {
+            return self::evaluateArrayArgumentsSubset([self::class, __FUNCTION__], 3, $x, $n, $m, ...$args);
+        }
+
+        try {
+            $x = Helpers::validateNumericNullSubstitution($x, 0);
+            $n = Helpers::validateNumericNullSubstitution($n, 0);
+            $m = Helpers::validateNumericNullSubstitution($m, 0);
+
+            // Loop through arguments
+            $aArgs = Functions::flattenArray($args);
+            $returnValue = 0;
+            $i = 0;
+            foreach ($aArgs as $argx) {
+                if ($argx !== null) {
+                    $arg = Helpers::validateNumericNullSubstitution($argx, 0);
+                    $returnValue += $arg * $x ** ($n + ($m * $i));
+                    ++$i;
+                }
+            }
+        } catch (Exception $e) {
+            return $e->getMessage();
+        }
+
+        return $returnValue;
+    }
+}