1. The on-line encyclopedia of integer sequences (OEIS), http://oeis.org.
2. PARI/GP, version 2.5.2, Bordeaux, 2013, http://pari.math.u-bordeaux.fr/.
3. Python, version 2.7.5 (2013), http://www.python.org.
4. Xcas 1.1.0 (c) 2000-14, Bernard Parisse, Renee De Graeve, http://www-fourier.ujf-grenoble.fr/~parisse/giac.html.
5. The least quadratic non residue;Ankeny;Ann. of Math. (2),1952