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.

A325192 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 square containing and the maximal square contained in the Young diagram is k.

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%I A325192 #12 Jan 12 2024 17:27:35
%S A325192 1,1,0,0,2,0,0,1,2,0,1,0,2,2,0,0,2,1,2,2,0,0,3,2,2,2,2,0,0,2,4,3,2,2,
%T A325192 2,0,0,1,7,4,4,2,2,2,0,1,0,6,8,5,4,2,2,2,0,0,2,5,11,8,6,4,2,2,2,0,0,3,
%U A325192 4,12,12,9,6,4,2,2,2,0,0,4,5,13,17,12,10,6,4,2,2,2,0
%N A325192 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 square containing and the maximal square contained in the Young diagram is k.
%C A325192 The maximal square contained in the Young diagram of an integer partition is called its Durfee square, and its length is the rank of the partition.
%D A325192 Richard P. Stanley, Enumerative Combinatorics, Volume 2,  Cambridge University Press, 1999, p. 289.
%H A325192 Andrew Howroyd, <a href="/A325192/b325192.txt">Table of n, a(n) for n = 0..1325</a> (rows 0..50)
%H A325192 Wikipedia, <a href="https://en.wikipedia.org/wiki/Durfee_square">Durfee square</a>.
%F A325192 Sum_{k=1..n} k*T(n,k) = A368985(n) - A115995(n). - _Andrew Howroyd_, Jan 12 2024
%e A325192 Triangle begins:
%e A325192   1
%e A325192   1  0
%e A325192   0  2  0
%e A325192   0  1  2  0
%e A325192   1  0  2  2  0
%e A325192   0  2  1  2  2  0
%e A325192   0  3  2  2  2  2  0
%e A325192   0  2  4  3  2  2  2  0
%e A325192   0  1  7  4  4  2  2  2  0
%e A325192   1  0  6  8  5  4  2  2  2  0
%e A325192   0  2  5 11  8  6  4  2  2  2  0
%e A325192   0  3  4 12 12  9  6  4  2  2  2  0
%e A325192   0  4  5 13 17 12 10  6  4  2  2  2  0
%e A325192   0  3  9 12 20 18 13 10  6  4  2  2  2  0
%e A325192   0  2 12 15 23 25 18 14 10  6  4  2  2  2  0
%e A325192   0  1 15 19 26 30 26 19 14 10  6  4  2  2  2  0
%e A325192 Row 9 counts the following partitions (empty columns not shown):
%e A325192    333   432    54      63       72        711       81         9
%e A325192          441    522     621      6111      3111111   21111111   111111111
%e A325192          3222   531     51111    411111
%e A325192          3321   5211    222111   2211111
%e A325192          4221   22221   321111
%e A325192          4311   32211
%e A325192                 33111
%e A325192                 42111
%t A325192 durf[ptn_]:=Length[Select[Range[Length[ptn]],ptn[[#]]>=#&]];
%t A325192 codurf[ptn_]:=Max[Length[ptn],Max[ptn]];
%t A325192 Table[Length[Select[IntegerPartitions[n],codurf[#]-durf[#]==k&]],{n,0,15},{k,0,n}]
%o A325192 (PARI) row(n)={my(r=vector(n+1)); if(n==0, r[1]=1, forpart(p=n, my(c=1); while(c<#p && c<p[#p-c], c++); r[max(#p,p[#p])-c+1]++)); r} \\ _Andrew Howroyd_, Jan 12 2024
%Y A325192 Row sums are A000041. Column k = 1 is A325181. Column k = 2 is A325182.
%Y A325192 Cf. A096771, A257990, A263297, A325178, A325179, A325180, A325200.
%Y A325192 Cf. A115995, A368985.
%K A325192 nonn,tabl
%O A325192 0,5
%A A325192 _Gus Wiseman_, Apr 08 2019