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diff --git a/printNumbers/functions/sumN.py b/printNumbers/functions/sumN.py
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+++ b/printNumbers/functions/sumN.py
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+# -*- coding: utf-8 -*-
+#
+# sumN.py
+#
+# This file is part of printNumbers.
+#
+# Copyright (C) 2017 G. Trensch, Simulation & Datalab Neuroscience, JSC, FZ Juelich
+#
+# printNumbers is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# printNumbers is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with printNumbers.  If not, see <http://www.gnu.org/licenses/>.
+
+import numpy as np
+
+def sumN(n):
+    '''
+    :param n:  Operand
+    :return:   sum from 1 to n
+    '''
+    return(np.sum(range(0,n+1)))
diff --git a/printNumbers/unittests/test_sumN.py b/printNumbers/unittests/test_sumN.py
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+++ b/printNumbers/unittests/test_sumN.py
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+# -*- coding: utf-8 -*-
+#
+# test_sumN.py
+#
+# This file is part of PrintNumbers.
+#
+# Copyright (C) 2017 G. Trensch, Simulation & Datalab Neuroscience, JSC, FZ Juelich
+#
+# PrintNumbers is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# PrintNumbers is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with PrintNumbers.  If not, see <http://www.gnu.org/licenses/>.
+
+#
+# Unit tests: 'sumN'.
+#
+
+import sys, os
+sys.path.append(os.path.join(os.path.dirname(__file__), '..'))
+
+import unittest
+from functions.sumN import *
+
+class TestsumN(unittest.TestCase):
+
+    def test_value_1(self):
+        self.assertEqual(sumN(1), [1] )
+
+    def test_value_5(self):
+        self.assertEqual(sumN(5), [15])
+
+    def test_value_3(self):
+        self.assertEqual(sumN(3), [6])
+
+
+def suite():
+    suite = unittest.makeSuite(TestsumN, 'test')
+    return suite
+
+def run():
+    runner = unittest.TextTestRunner(verbosity = 2)
+    runner.run(suite())
+
+if __name__ == "__main__":
+    run()