OFFSET
0,2
COMMENTS
Also the number of ascending runs of length n+3 in the permutations of [2n+3].
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..300
FORMULA
MAPLE
a:= proc(n) option remember; `if`(n<2, 1+7*n, 2*(2*n+3)*(n+1)*
(n^3+8*n^2+20*n+19)*a(n-1)/((n+5)*(n^3+5*n^2+7*n+6)))
end:
seq(a(n), n=0..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 16 2013
STATUS
approved