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Triangle read by rows where T(n,k) is the number of integer partitions of n with median k, where k ranges from 1 to n in steps of 1/2.
132

%I #7 Jan 22 2023 09:16:56

%S 1,1,0,1,1,1,0,0,1,2,0,2,0,0,0,1,3,0,1,2,0,0,0,0,1,4,1,2,0,3,0,0,0,0,

%T 0,1,6,1,3,0,1,3,0,0,0,0,0,0,1,8,1,6,0,2,0,4,0,0,0,0,0,0,0,1,11,2,7,1,

%U 3,0,1,4,0,0,0,0,0,0,0,0,1

%N Triangle read by rows where T(n,k) is the number of integer partitions of n with median k, where k ranges from 1 to n in steps of 1/2.

%C The median of a multiset is either the middle part (for odd length), or the average of the two middle parts (for even length).

%e Triangle begins:

%e 1

%e 1 0 1

%e 1 1 0 0 1

%e 2 0 2 0 0 0 1

%e 3 0 1 2 0 0 0 0 1

%e 4 1 2 0 3 0 0 0 0 0 1

%e 6 1 3 0 1 3 0 0 0 0 0 0 1

%e 8 1 6 0 2 0 4 0 0 0 0 0 0 0 1

%e 11 2 7 1 3 0 1 4 0 0 0 0 0 0 0 0 1

%e 15 2 10 3 4 0 2 0 5 0 0 0 0 0 0 0 0 0 1

%e 20 3 13 3 7 0 3 0 1 5 0 0 0 0 0 0 0 0 0 0 1

%e 26 4 19 3 11 1 4 0 2 0 6 0 0 0 0 0 0 0 0 0 0 0 1

%e For example, row n = 8 counts the following partitions:

%e 611 4211 422 . 332 . 44 . . . . . . . 8

%e 5111 521 431 53

%e 32111 2222 62

%e 41111 3221 71

%e 221111 3311

%e 311111 22211

%e 2111111

%e 11111111

%t Table[Length[Select[IntegerPartitions[n], Median[#]==k&]],{n,1,10},{k,1,n,1/2}]

%Y Row sums are A000041.

%Y Row lengths are 2n-1 = A005408(n-1).

%Y Column k=1 is A027336(n+1).

%Y For mean instead of median we have A058398, see also A008284, A327482.

%Y The mean statistic is ranked by A326567/A326568.

%Y Omitting half-steps gives A359901.

%Y The odd-length case is A359902.

%Y The median statistic is ranked by A360005(n)/2.

%Y First appearances of medians are ranked by A360006, A360007.

%Y A027193 counts odd-length partitions, strict A067659, ranked by A026424.

%Y A067538 counts partitions w/ integer mean, strict A102627, ranked by A316413.

%Y A240219 counts partitions w/ the same mean as median, complement A359894.

%Y Cf. A325347, A349156, A359889, A359895, A359906, A359907, A360008.

%K nonn,tabf

%O 1,10

%A _Gus Wiseman_, Jan 21 2023