login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Number of permutations of {1..n} with fewer than 7 interior elements having values lying between the values of their neighbors.
1

%I #8 Jul 17 2024 18:53:05

%S 1,1,2,6,24,120,720,5040,40320,362878,3627778,39830282,475089392,

%T 6094561180,83333937940,1205398303180,18331873363480,291706615484450,

%U 4838414115229430,83404373736108502,1490681666580459304,27572241018065482032,526959942343051879032

%N Number of permutations of {1..n} with fewer than 7 interior elements having values lying between the values of their neighbors.

%H Alois P. Heinz, <a href="/A226440/b226440.txt">Table of n, a(n) for n = 0..480</a> (terms n = 1..206 from R. H. Hardin)

%e Some solutions for n=7

%e ..2....2....2....1....7....2....6....4....2....2....7....1....1....4....6....4

%e ..5....3....1....7....4....3....7....2....1....7....3....3....5....3....3....5

%e ..3....7....6....2....5....6....2....1....5....6....5....4....4....2....2....6

%e ..4....1....4....4....2....7....1....5....6....4....6....6....7....1....4....2

%e ..7....4....3....3....3....4....4....3....4....5....2....7....3....5....7....3

%e ..1....6....5....5....6....1....5....6....3....3....1....2....2....6....1....7

%e ..6....5....7....6....1....5....3....7....7....1....4....5....6....7....5....1

%Y Column 7 of A226441.

%K nonn

%O 0,3

%A _R. H. Hardin_, Jun 06 2013

%E a(0)=1 prepended by _Alois P. Heinz_, Jul 17 2024