OFFSET
1,2
LINKS
Elena Barcucci, Alberto Del Lungo, Elisa Pergola, Renzo Pinzani, Permutations avoiding an increasing number of length-increasing forbidden subsequences, Discrete Mathematics and Theoretical Computer Science 4, 2000, 31-44
FORMULA
f := (x, j)->1-(j+1)*x- sqrt(1-2*(j+1)*x+(j-1)^2*x^2); t := (x, j)->sum(k!*x^k, k=1..(j-1)); s := (x, j)->x^(j-2)*(j-1)!*(f(x, j))/(2)+ t(x, j); j := 6
CROSSREFS
KEYWORD
nonn
AUTHOR
Elisa Pergola (elisa(AT)dsi.unifi.it), May 26 2000
STATUS
approved