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%I #5 Nov 14 2015 16:57:36
%S 55,1393,22180,290341,3443222,39212955,439762906,4922646194,
%T 55440198721,631281758915,7290146619344,85550258610256,
%U 1021466597564828,12418915430929303,153814790549535203,1941191617618161308,24964754218212162461,327159226788279647296
%N Number of permutations of [n] with exactly eight (possibly overlapping) occurrences of the generalized pattern 23-1.
%H Alois P. Heinz, <a href="/A264467/b264467.txt">Table of n, a(n) for n = 7..500</a>
%e a(7) = 55: 2567341, 3456712, 3456721, ..., 6745213, 6745312, 6745321.
%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, 9), polynom), j=1..o))
%p end:
%p a:= n-> coeff(b(n, 0), x, 8):
%p seq(a(n), n=7..25);
%Y Column k=8 of A260670.
%K nonn
%O 7,1
%A _Alois P. Heinz_, Nov 14 2015
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