OFFSET
0,2
COMMENTS
Also the number of ascending runs of length n+2 in the permutations of [2n+2].
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..300
FORMULA
MAPLE
a:= proc(n) option remember; `if`(n<2, 1+5*n, 2*(n+1)*(2*n+1)*
(n^3+6*n^2+12*n+11)*a(n-1)/((n+4)*(n^3+3*n^2+3*n+4)))
end:
seq(a(n), n=0..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 16 2013
STATUS
approved