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%I
%S 4,20,108,586,3098,16230,85150,446972,2349616,12376800,65353448,
%T 345933358,1835637246,9764363438,52064375292,278256581910,
%U 1490475179006,8000983513636,43039329754332,231982689315468,1252791611642654,6777998215153164,36735901427197962
%N Number of permutations p of [n] such that in 0p the largest up-jump equals four and no down-jump is larger than 2.
%H Alois P. Heinz, <a href="/A321111/b321111.txt">Table of n, a(n) for n = 4..1000</a>
%p b:= proc(u, o, k) option remember; `if`(u+o=0, 1,
%p add(b(u-j, o+j-1, k), j=1..min(2, u))+
%p add(b(u+j-1, o-j, k), j=1..min(k, o)))
%p end:
%p a:= n-> (k-> b(0, n, k)-b(0, n, k-1))(4):
%p seq(a(n), n=4..30);
%Y Column k=4 of A291680.
%K nonn
%O 4,1
%A _Alois P. Heinz_, Oct 27 2018
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