A264462 Number of permutations of [n] with exactly three (possibly overlapping) occurrences of the generalized pattern 23-1.

10, 98, 791, 6082, 46508, 360376, 2855580, 23244370, 194796665, 1682243510, 14973751272, 137345968648, 1297620307926, 12620234271634, 126265094967383, 1298634572382618, 13720327052477584, 148800093788609512, 1655374072150829472, 18877499531817214482

Offset: 5

Author

Alois P. Heinz, Nov 14 2015

Keywords

• nonn

Examples

			a(5) = 10: 23451, 24513, 24531, 34251, 35241, 45123, 45132, 45213, 45312, 45321.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 5..500

Crossrefs

Column k=3 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, 4), polynom), j=1..o))
    end:
a:= n-> coeff(b(n, 0), x, 3):
seq(a(n), n=5..25);