A117514 Number of ways of arranging 2n tokens in a row, with 2 copies of each token from 1 through n, such that the first token is a 1 and between every pair of tokens labeled i (i=1..n) there is exactly one taken labeled (i+1 mod n).
1, 1, 2, 18, 248, 5560, 174752
Offset: 1