add Sister Celine's method

[sagetrac-ktkohl]

Sister Celine's algorithm computes "k-free" recurrences for hypergeometric terms and sums.

http://mathworld.wolfram.com/SisterCelinesMethod.html

Add these functions:

• to verify that a term is hypergeometric
• to find recurrence for the summand
• to sum over the recurrence found above

CC: @rwst @fredrik-johansson

Component: symbolics

Keywords: hypergeometric, series, recurrences

Author: Karen Kohl

Issue created by migration from https://trac.sagemath.org/ticket/19149

[rwst]

comment:1

Hi Karen, the Author: trac ticket field specifies the author of the code (if such is present). If you only want to report the ticket your authorship is specified in the Reported by: field automatically.

[jdemeyer]

comment:2

In other words, the fact that you wrote "Karen Kohl" as Author implies to me that you are actually going to work on this ticket.