A325200 Regular triangle read by rows where T(n,k) is the number of integer partitions of n such that the difference between the length of the minimal triangular partition containing and the maximal triangular partition contained in the Young diagram is k.

1, 1, 0, 0, 2, 0, 1, 0, 2, 0, 0, 3, 0, 2, 0, 0, 3, 2, 0, 2, 0, 1, 0, 6, 2, 0, 2, 0, 0, 4, 3, 4, 2, 0, 2, 0, 0, 6, 2, 6, 4, 2, 0, 2, 0, 0, 4, 9, 5, 4, 4, 2, 0, 2, 0, 1, 0, 15, 6, 8, 4, 4, 2, 0, 2, 0, 0, 5, 12, 12, 9, 6, 4, 4, 2, 0, 2, 0, 0, 10, 6, 21, 10, 12, 6, 4, 4, 2, 0, 2, 0

Offset

0,5

Links

Andrew Howroyd, Table of n, a(n) for n = 0..1325 (rows 0..50)

FindStat, St000380: Half the perimeter of the largest rectangle that fits inside the diagram of an integer partition

FindStat, St000384: The maximal part of the shifted composition of an integer partition

FindStat, St000783: The maximal number of occurrences of a colour in a proper colouring of a Ferrers diagram

Formula

Sum_{k=1..n} k*T(n,k) = A366157(n) - A368986(n). - Andrew Howroyd, Jan 13 2024

Example

Triangle begins:
  1
  1  0
  0  2  0
  1  0  2  0
  0  3  0  2  0
  0  3  2  0  2  0
  1  0  6  2  0  2  0
  0  4  3  4  2  0  2  0
  0  6  2  6  4  2  0  2  0
  0  4  9  5  4  4  2  0  2  0
  1  0 15  6  8  4  4  2  0  2  0
  0  5 12 12  9  6  4  4  2  0  2  0
  0 10  6 21 10 12  6  4  4  2  0  2  0
  0 10 12 20 18 13 10  6  4  4  2  0  2  0
  0  5 27 20 23 16 16 10  6  4  4  2  0  2  0
  1  0 38 22 32 22 19 14 10  6  4  4  2  0  2  0
  0  6 34 38 34 35 20 22 14 10  6  4  4  2  0  2  0
  0 15 22 57 44 40 34 23 20 14 10  6  4  4  2  0  2  0
  0 20 20 71 55 54 45 32 26 20 14 10  6  4  4  2  0  2  0
  0 15 43 70 71 66 60 44 35 24 20 14 10  6  4  4  2  0  2  0
  0  6 74 64 99 83 70 65 42 38 24 20 14 10  6  4  4  2  0  2  0
Row n = 9 counts the following partitions (empty columns not shown):
  (432)   (333)    (54)      (63)      (72)       (81)        (9)
  (3321)  (441)    (621)     (6111)    (711)      (21111111)  (111111111)
  (4221)  (522)    (22221)   (222111)  (2211111)
  (4311)  (531)    (51111)   (411111)  (3111111)
          (3222)   (321111)
          (5211)
          (32211)
          (33111)
          (42111)

Mathematica

otb[ptn_]:=Min@@MapIndexed[#1+#2[[1]]-1&, Append[ptn, 0]];
otbmax[ptn_]:=Max@@MapIndexed[#1+#2[[1]]-1&, Append[ptn, 0]];
Table[Length[Select[IntegerPartitions[n], otbmax[#]-otb[#]==k&]], {n, 0, 20}, {k, 0, n}]

Prog

(PARI) row(n)={my(r=vector(n+1)); forpart(p=n, my(b=#p, c=0); for(i=1, #p, my(x=#p-i+p[i]); b=min(b, x); c=max(c, x)); r[c-b+1]++); r} \\ Andrew Howroyd, Jan 12 2024

Crossrefs

Row sums are A000041. Column k = 1 is A325191. Column k = 2 is A325199.

T(n,k) = A325189(n,k) - A325188(n,k).

Cf. A046660, A065770, A071724, A243055, A325169, A325178, A325195, A325196, A325197, A366157, A368986.

Sequence in context: A352555 A307831 A217564 * A266909 A276491 A035177

Adjacent sequences: A325197 A325198 A325199 * A325201 A325202 A325203

Keyword

nonn,tabl

Author

Gus Wiseman, Apr 11 2019

Status

approved