See http://mathworld.wolfram.com/RecurrenceEquation.html.

See http://www.math2.org/math/general/interest.htm.

Historical information and papers about the Tower of Hanoi are at http://www.cs.wm.edu/~pkstoc/toh.html. An interactive version of the Tower of Hanoi and other information are at http://www.lhs.berkeley.edu/Java/Tower/towerhistory.html. Another interactive version is at http://www.mazeworks.com/hanoi/index.htm. My own source code for a text-based simulation is tower.c. A biography of Lucas is at http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Lucas.html.

A biography of Ackermann is at http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Ackermann.html.

See http://www.math.uvic.ca/faculty/gmacgill/guide/solvingrec.pdf.

An animation of selection sort and other algorithms can be found at http://www.inf.ethz.ch/~staerk/algorithms/SortAnimation.html.

An animation of merge sort and other algorithms can be found at http://www.cs.princeton.edu/~ah/alg_anim/version2/Animations.html and http://www.inf.ethz.ch/~staerk/algorithms/SortAnimation.html.