cp's OEIS Frontend

A201375 T(n,k)=Number of nXk 0..1 arrays with rows and columns lexicographically nondecreasing read forwards, and nonincreasing read backwards.

%I A201375 #7 Jul 22 2025 16:12:20
%S A201375 2,2,2,2,3,2,2,4,4,2,2,5,8,5,2,2,6,14,14,6,2,2,7,22,36,22,7,2,2,8,32,
%T A201375 80,80,32,8,2,2,9,44,157,268,157,44,9,2,2,10,58,280,786,786,280,58,10,
%U A201375 2,2,11,74,464,2016,3739,2016,464,74,11,2,2,12,92,726,4608,15574,15574,4608
%N A201375 T(n,k)=Number of nXk 0..1 arrays with rows and columns lexicographically nondecreasing read forwards, and nonincreasing read backwards.
%C A201375 Table starts
%C A201375 .2..2..2....2.....2......2........2.........2...........2............2
%C A201375 .2..3..4....5.....6......7........8.........9..........10...........11
%C A201375 .2..4..8...14....22.....32.......44........58..........74...........92
%C A201375 .2..5.14...36....80....157......280.......464.........726.........1085
%C A201375 .2..6.22...80...268....786.....2016......4608........9582........18446
%C A201375 .2..7.32..157...786...3739....15574.....55410......170616.......465037
%C A201375 .2..8.44..280..2016..15574...115168....728078.....3793342.....16517460
%C A201375 .2..9.58..464..4608..55410...728078...8866257....88486476....701948916
%C A201375 .2.10.74..726..9582.170616..3793342..88486476..1799674094..28852930912
%C A201375 .2.11.92.1085.18446.465037.16517460.701948916.28852930912.976134459840
%H A201375 R. H. Hardin, <a href="/A201375/b201375.txt">Table of n, a(n) for n = 1..220</a>
%e A201375 Some solutions for n=7 k=5
%e A201375 ..0..0..0..1..1....0..0..0..1..1....0..0..1..1..1....0..0..0..1..1
%e A201375 ..0..0..0..1..1....0..0..0..1..1....0..1..0..1..1....0..0..0..1..1
%e A201375 ..0..0..0..1..1....1..1..1..0..1....0..1..1..0..1....0..1..1..0..1
%e A201375 ..0..0..1..0..1....1..1..1..0..1....0..1..1..0..1....1..0..1..0..1
%e A201375 ..0..1..0..0..1....1..1..1..1..0....0..1..1..1..0....1..0..1..1..0
%e A201375 ..1..0..0..0..1....1..1..1..1..0....0..1..1..1..0....1..1..0..0..0
%e A201375 ..1..1..1..1..0....1..1..1..1..0....1..0..0..0..0....1..1..0..0..0
%Y A201375 Column 3 is A003682
%K A201375 nonn,tabl
%O A201375 1,1
%A A201375 _R. H. Hardin_ Nov 30 2011