A264456 Number of permutations of [n] with exactly seven (possibly overlapping) occurrences of the generalized pattern 12-3.

5, 122, 1960, 25922, 308912, 3488684, 38438284, 420224213, 4604712333, 50891058160, 569534211553, 6470640729869, 74755213239764, 879145839345147, 10531462769901577, 128554339635477023, 1599307831822386125, 20278763016658278490, 262052769447634167173

Offset: 6

Author

Alois P. Heinz, Nov 14 2015

Keywords

• nonn

Examples

			a(6) = 5: 123645, 123654, 124356, 124536, 124563.
a(7) = 122: 1253746, 1253764, 1254376, ..., 7124356, 7124536, 7124563.
		

Links

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

Crossrefs

Column k=7 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, 8), polynom), j=1..o))
    end:
a:= n-> coeff(b(n, 0), x, 7):
seq(a(n), n=6..25);