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

%I A264465 #7 Nov 14 2015 16:49:33
%S A264465 11,240,3328,36774,377610,3775281,37545239,375714151,3808210872,
%T A264465 39250117725,412320359485,4420852570619,48416817503118,
%U A264465 541846406216437,6197311080340307,72436698579083259,865110836456018947,10554489471399030408,131500190867301682844
%N A264465 Number of permutations of [n] with exactly six (possibly overlapping) occurrences of the generalized pattern 23-1.
%H A264465 Alois P. Heinz, <a href="/A264465/b264465.txt">Table of n, a(n) for n = 6..500</a>
%e A264465 a(6) = 11: 345612, 345621, 356241, 456123, 456132, 456213, 456312, 456321, 562341, 563412, 563421.
%p A264465 b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
%p A264465       b(u-j, o+j-1), j=1..u) +add(convert(series(
%p A264465       b(u+j-1, o-j)*x^u, x, 7), polynom), j=1..o))
%p A264465     end:
%p A264465 a:= n-> coeff(b(n, 0), x, 6):
%p A264465 seq(a(n), n=6..25);
%Y A264465 Column k=6 of A260670.
%K A264465 nonn
%O A264465 6,1
%A A264465 _Alois P. Heinz_, Nov 14 2015