A264457 Number of permutations of [n] with exactly eight (possibly overlapping) occurrences of the generalized pattern 12-3.

2, 68, 1303, 19637, 259676, 3187742, 37608672, 435669452, 5021292420, 58054439247, 676861345712, 7985430177542, 95546837440564, 1161199181184289, 14348225375153127, 180370057811385955, 2307651822107975903, 30054039071752083133, 398467881283163344126

Offset: 6

Author

Alois P. Heinz, Nov 14 2015

Keywords

• nonn

Examples

			a(6) = 2: 123546, 123564.
a(7) = 68: 1243756, 1243765, 1247365, ..., 6123574, 7123546, 7123564.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 6..500

Crossrefs

Column k=8 of A260665.

Programs

Maple

b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
       b(u-j, o+j-1), j=1..u)+add(convert(series(
       b(u+j-1, o-j)*x^(o-j), x, 9), polynom), j=1..o))
    end:
a:= n-> coeff(b(n, 0), x, 8):
seq(a(n), n=6..25);