cp's OEIS Frontend

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

%I A264463 #5 Nov 14 2015 16:45:05
%S A264463 3,62,624,5513,46880,396545,3388893,29497132,262619041,2397130075,
%T A264463 22458202716,216063700398,2134707078315,21655074753266,
%U A264463 225471830153938,2408463527492433,26380434283682048,296130434080550183,3404883834560222589,40077202708717399396
%N A264463 Number of permutations of [n] with exactly four (possibly overlapping) occurrences of the generalized pattern 23-1.
%H A264463 Alois P. Heinz, <a href="/A264463/b264463.txt">Table of n, a(n) for n = 5..500</a>
%e A264463 a(5) = 3: 34512, 34521, 45231.
%p A264463 b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
%p A264463       b(u-j, o+j-1), j=1..u) +add(convert(series(
%p A264463       b(u+j-1, o-j)*x^u, x, 5), polynom), j=1..o))
%p A264463     end:
%p A264463 a:= n->  coeff(b(n, 0), x, 4):
%p A264463 seq(a(n), n=5..25);
%Y A264463 Column k=4 of A260670.
%K A264463 nonn
%O A264463 5,1
%A A264463 _Alois P. Heinz_, Nov 14 2015