A264465 Number of permutations of [n] with exactly six (possibly overlapping) occurrences of the generalized pattern 23-1.

11, 240, 3328, 36774, 377610, 3775281, 37545239, 375714151, 3808210872, 39250117725, 412320359485, 4420852570619, 48416817503118, 541846406216437, 6197311080340307, 72436698579083259, 865110836456018947, 10554489471399030408, 131500190867301682844

Offset: 6

Author

Alois P. Heinz, Nov 14 2015

Keywords

• nonn

Examples

			a(6) = 11: 345612, 345621, 356241, 456123, 456132, 456213, 456312, 456321, 562341, 563412, 563421.
		

Links

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

Crossrefs

Column k=6 of A260670.

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^u, x, 7), polynom), j=1..o))
    end:
a:= n-> coeff(b(n, 0), x, 6):
seq(a(n), n=6..25);