A264463 Number of permutations of [n] with exactly four (possibly overlapping) occurrences of the generalized pattern 23-1.

3, 62, 624, 5513, 46880, 396545, 3388893, 29497132, 262619041, 2397130075, 22458202716, 216063700398, 2134707078315, 21655074753266, 225471830153938, 2408463527492433, 26380434283682048, 296130434080550183, 3404883834560222589, 40077202708717399396

Offset: 5

Author

Alois P. Heinz, Nov 14 2015

Keywords

• nonn

Examples

			a(5) = 3: 34512, 34521, 45231.
		

Links

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

Crossrefs

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