cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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.

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%I A325200 #16 Jan 13 2024 13:08:45
%S A325200 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,
%T A325200 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,
%U A325200 12,12,9,6,4,4,2,0,2,0,0,10,6,21,10,12,6,4,4,2,0,2,0
%N 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.
%H A325200 Andrew Howroyd, <a href="/A325200/b325200.txt">Table of n, a(n) for n = 0..1325</a> (rows 0..50)
%H A325200 FindStat, <a href="http://www.findstat.org/StatisticsDatabase/St000380">St000380: Half the perimeter of the largest rectangle that fits inside the diagram of an integer partition</a>
%H A325200 FindStat, <a href="http://www.findstat.org/StatisticsDatabase/St000384">St000384: The maximal part of the shifted composition of an integer partition</a>
%H A325200 FindStat, <a href="http://www.findstat.org/StatisticsDatabase/St000783">St000783: The maximal number of occurrences of a colour in a proper colouring of a Ferrers diagram</a>
%F A325200 Sum_{k=1..n} k*T(n,k) = A366157(n) - A368986(n). - _Andrew Howroyd_, Jan 13 2024
%e A325200 Triangle begins:
%e A325200   1
%e A325200   1  0
%e A325200   0  2  0
%e A325200   1  0  2  0
%e A325200   0  3  0  2  0
%e A325200   0  3  2  0  2  0
%e A325200   1  0  6  2  0  2  0
%e A325200   0  4  3  4  2  0  2  0
%e A325200   0  6  2  6  4  2  0  2  0
%e A325200   0  4  9  5  4  4  2  0  2  0
%e A325200   1  0 15  6  8  4  4  2  0  2  0
%e A325200   0  5 12 12  9  6  4  4  2  0  2  0
%e A325200   0 10  6 21 10 12  6  4  4  2  0  2  0
%e A325200   0 10 12 20 18 13 10  6  4  4  2  0  2  0
%e A325200   0  5 27 20 23 16 16 10  6  4  4  2  0  2  0
%e A325200   1  0 38 22 32 22 19 14 10  6  4  4  2  0  2  0
%e A325200   0  6 34 38 34 35 20 22 14 10  6  4  4  2  0  2  0
%e A325200   0 15 22 57 44 40 34 23 20 14 10  6  4  4  2  0  2  0
%e A325200   0 20 20 71 55 54 45 32 26 20 14 10  6  4  4  2  0  2  0
%e A325200   0 15 43 70 71 66 60 44 35 24 20 14 10  6  4  4  2  0  2  0
%e A325200   0  6 74 64 99 83 70 65 42 38 24 20 14 10  6  4  4  2  0  2  0
%e A325200 Row n = 9 counts the following partitions (empty columns not shown):
%e A325200   (432)   (333)    (54)      (63)      (72)       (81)        (9)
%e A325200   (3321)  (441)    (621)     (6111)    (711)      (21111111)  (111111111)
%e A325200   (4221)  (522)    (22221)   (222111)  (2211111)
%e A325200   (4311)  (531)    (51111)   (411111)  (3111111)
%e A325200           (3222)   (321111)
%e A325200           (5211)
%e A325200           (32211)
%e A325200           (33111)
%e A325200           (42111)
%t A325200 otb[ptn_]:=Min@@MapIndexed[#1+#2[[1]]-1&,Append[ptn,0]];
%t A325200 otbmax[ptn_]:=Max@@MapIndexed[#1+#2[[1]]-1&,Append[ptn,0]];
%t A325200 Table[Length[Select[IntegerPartitions[n],otbmax[#]-otb[#]==k&]],{n,0,20},{k,0,n}]
%o A325200 (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
%Y A325200 Row sums are A000041. Column k = 1 is A325191. Column k = 2 is A325199.
%Y A325200 T(n,k) = A325189(n,k) - A325188(n,k).
%Y A325200 Cf. A046660, A065770, A071724, A243055, A325169, A325178, A325195, A325196, A325197, A366157, A368986.
%K A325200 nonn,tabl
%O A325200 0,5
%A A325200 _Gus Wiseman_, Apr 11 2019