OFFSET
1,1
REFERENCES
R. K. Guy, Building Barrycades, preprint, 2006
R. K. Guy, Building Barrycades and Constructing Corrals, in "Barrycades and Septoku: Papers in Honor of Martin Gardner and Tom Rogers", ed. Thane Plambeck and Tomas Rokicki, MAA Press, 2020, pp. 11-18
EXAMPLE
a(2)=8 since there are eight permutations of (1,2,3,4) satisfying the Fink condition: (1,3,4,2), (1,4,2,3), (1,4,3,2), (2,4,1,3) and their mirror images.
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Kevin Saff (kevin.saff(AT)gmail.com), Mar 11 2007
EXTENSIONS
a(9)-a(13) from Don Knuth, Aug 24 2020
STATUS
approved