PREFIX math: <http://www.w3.org/2000/10/swap/math#>
PREFIX list: <http://www.w3.org/2000/10/swap/list#>
PREFIX func: <http://www.w3.org/2007/rif-builtin-function#>
PREFIX e: <http://eulersharp.sourceforge.net/2003/03swap/log-rules#>
PREFIX seq: <http://josd.github.io/eye/reasoning/seq#>
PREFIX string: <http://www.w3.org/2000/10/swap/string#>

(1 2 3 4 6 9 10 11 13) seq:answer "1-4, 6, 9-11, 13".

