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A264464 Number of permutations of [n] with exactly five (possibly overlapping) occurrences of the generalized pattern 23-1.

%I A264464 #7 Nov 14 2015 16:51:24
%S A264464 22,392,4302,41979,393476,3652779,34099448,322746351,3111556310,
%T A264464 30637025849,308542096284,3180677263083,33574281993047,
%U A264464 362907367462521,4016295885663247,45496983534864142,527373693673894161,6252643277063017082,75794122449729562363
%N A264464 Number of permutations of [n] with exactly five (possibly overlapping) occurrences of the generalized pattern 23-1.
%H A264464 Alois P. Heinz, <a href="/A264464/b264464.txt">Table of n, a(n) for n = 6..500</a>
%e A264464 a(6) = 22: 245613, 245631, 256341, 345261, 346251, 356124, 356142, 356214, 356412, 356421, 452361, 453612, 453621, 462351, 463512, 463521, 561342, 562314, 562413, 562431, 563241, 564231.
%p A264464 b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
%p A264464       b(u-j, o+j-1), j=1..u) +add(convert(series(
%p A264464       b(u+j-1, o-j)*x^u, x, 6), polynom), j=1..o))
%p A264464     end:
%p A264464 a:= n-> coeff(b(n, 0), x, 5):
%p A264464 seq(a(n), n=6..25);
%Y A264464 Column k=5 of A260670.
%K A264464 nonn
%O A264464 6,1
%A A264464 _Alois P. Heinz_, Nov 14 2015