cp's OEIS Frontend

A264468 Number of permutations of [n] with exactly nine (possibly overlapping) occurrences of the generalized pattern 23-1.

%I A264468 #5 Nov 14 2015 16:59:29
%S A264468 18,780,15627,235045,3086010,37816568,449766437,5291113080,
%T A264468 62237008779,736806459069,8816027319934,106900514193980,
%U A264468 1315953951437664,16464756848575162,209528329365176670,2713295547732215190,35762229764646245816,479809424452611001696
%N A264468 Number of permutations of [n] with exactly nine (possibly overlapping) occurrences of the generalized pattern 23-1.
%H A264468 Alois P. Heinz, <a href="/A264468/b264468.txt">Table of n, a(n) for n = 7..500</a>
%e A264468 a(7) = 18: 3567241, 4567123, 4567132, 4567213, 4567312, 4567321, 4672351, 4673512, 4673521, 5671342, 5672314, 5672413, 5672431, 5673241, 5674231, 6734512, 6734521, 6745231.
%p A264468 b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
%p A264468       b(u-j, o+j-1), j=1..u) +add(convert(series(
%p A264468       b(u+j-1, o-j)*x^u, x, 10), polynom), j=1..o))
%p A264468     end:
%p A264468 a:= n-> coeff(b(n, 0), x, 9):
%p A264468 seq(a(n), n=7..25);
%Y A264468 Column k=9 of A260670.
%K A264468 nonn
%O A264468 7,1
%A A264468 _Alois P. Heinz_, Nov 14 2015