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%I #5 Nov 14 2015 16:55:23
%S 1,111,2141,29066,336137,3663730,39037155,414003430,4414401391,
%T 47606401475,521147444815,5804080039932,65854473968668,
%U 761861585833395,8990938684395442,108258685340444377,1330041483208589743,16671576238569453924,213169773223813966680
%N Number of permutations of [n] with exactly seven (possibly overlapping) occurrences of the generalized pattern 23-1.
%H Alois P. Heinz, <a href="/A264466/b264466.txt">Table of n, a(n) for n = 6..500</a>
%e a(6) = 1: 456231.
%e a(7) = 111: 1567342, 2456713, 2456731, ..., 6753412, 6753421, 7456231.
%p b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
%p b(u-j, o+j-1), j=1..u) +add(convert(series(
%p b(u+j-1, o-j)*x^u, x, 8), polynom), j=1..o))
%p end:
%p a:= n-> coeff(b(n, 0), x, 7):
%p seq(a(n), n=6..25);
%Y Column k=7 of A260670.
%K nonn
%O 6,2
%A _Alois P. Heinz_, Nov 14 2015
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