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 A362260 Maximum over 0 <= k <= n/2 of the number of permutations of two symbols occurring k and n-2*k times, respectively, where a permutation and its reversal are counted only once. 2

%I #12 Oct 26 2023 09:54:41

%S 1,1,1,1,2,2,4,6,9,12,19,28,44,66,110,170,255,396,651,1001,1519,2520,

%T 4032,6216,9752,15912,25236,38760,63090,101850,160050,248710,408760,

%U 653752,1021735,1634776,2656511,4218786,6562556,10737090,17299646,27313650,43249115

%N Maximum over 0 <= k <= n/2 of the number of permutations of two symbols occurring k and n-2*k times, respectively, where a permutation and its reversal are counted only once.

%C Also, a(n) is the maximum number of ways in which a set of integer-sided squares can tile an n X 2 rectangle, up to rotations and reflections.

%H Robert Israel, <a href="/A362260/b362260.txt">Table of n, a(n) for n = 0..4771</a>

%F a(n) >= A073028(n)/2.

%e For n = 8, the maximum a(8) = 9 is obtained for k = 2. The corresponding permutations of 2 2's and 4 1's are 221111, 212111, 211211, 211121, 211112, 122111, 121211, 121121, and 112211.

%p f:= proc(n) local k, v, m,w;

%p m:= 0:

%p for k from 0 to n/2 do

%p v:= binomial(n-k,k);

%p if n:: even and k::even then w:= binomial((n-k)/2,k/2)

%p elif (n-k)::odd then w:=binomial((n-k-1)/2, floor(k/2))

%p else w:= 0

%p fi;

%p m:= max(m,(v+w)/2);

%p od;

%p m

%p end proc:

%p map(f, [\$0..50]); # _Robert Israel_, Oct 25 2023

%Y Row maxima of A102541.

%Y Second column of A362258.

%Y Cf. A001224, A073028, A361224 (rectangular pieces).

%K nonn

%O 0,5

%A _Pontus von BrÃ¶mssen_, Apr 15 2023

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Last modified September 12 12:42 EDT 2024. Contains 375851 sequences. (Running on oeis4.)