cp's OEIS Frontend

A264455 Number of permutations of [n] with exactly six (possibly overlapping) occurrences of the generalized pattern 12-3.

%I A264455 #6 Nov 14 2015 08:24:12
%S A264455 1,17,238,2956,33343,355182,3681762,37839385,389940538,4056942189,
%T A264455 42796503464,458995025669,5013561835833,55832699192796,
%U A264455 634322118799677,7354538207075076,87032355679553323,1051183375285792257,12956782873283747998,162950022525866642259
%N A264455 Number of permutations of [n] with exactly six (possibly overlapping) occurrences of the generalized pattern 12-3.
%H A264455 Alois P. Heinz, <a href="/A264455/b264455.txt">Table of n, a(n) for n = 5..500</a>
%e A264455 a(5) = 1: 12345.
%e A264455 a(6) = 17: 124365, 124635, 124653, 125346, 132456, 134256, 134526, 134562, 213456, 231456, 234156, 234516, 234561, 312456, 412356, 512346, 612345.
%p A264455 b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
%p A264455        b(u-j, o+j-1), j=1..u)+add(convert(series(
%p A264455        b(u+j-1, o-j)*x^(o-j), x, 7), polynom), j=1..o))
%p A264455     end:
%p A264455 a:= n-> coeff(b(n, 0), x, 6):
%p A264455 seq(a(n), n=5..25);
%Y A264455 Column k=6 of A260665.
%K A264455 nonn
%O A264455 5,2
%A A264455 _Alois P. Heinz_, Nov 14 2015