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.

A325165 Regular triangle read by rows where T(n,k) is the number of integer partitions of n whose inner lining partition has last (smallest) part equal to k.

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%I A325165 #9 Jan 19 2023 12:31:02
%S A325165 1,0,1,0,0,2,0,0,0,3,0,1,0,0,4,0,2,0,0,0,5,0,3,2,0,0,0,6,0,4,4,0,0,0,
%T A325165 0,7,0,5,6,3,0,0,0,0,8,0,7,8,6,0,0,0,0,0,9,0,9,10,9,4,0,0,0,0,0,10,0,
%U A325165 13,12,12,8,0,0,0,0,0,0,11
%N A325165 Regular triangle read by rows where T(n,k) is the number of integer partitions of n whose inner lining partition has last (smallest) part equal to k.
%C A325165 The k-th part of the inner lining partition of an integer partition is the number of squares in its Young diagram that are k diagonal steps from the lower-right boundary. For example, the partition (6,5,5,3) has diagram
%C A325165   o o o o o o
%C A325165   o o o o o
%C A325165   o o o o o
%C A325165   o o o
%C A325165 which has diagonal distances from the lower-right boundary equal to
%C A325165   3 3 3 2 1 1
%C A325165   3 2 2 2 1
%C A325165   2 2 1 1 1
%C A325165   1 1 1
%C A325165 so the inner lining sequence is (9,6,4) with last part 4, so (6,5,5,3) is counted under T(19,4).
%H A325165 Andrew Howroyd, <a href="/A325165/b325165.txt">Table of n, a(n) for n = 0..1325</a> (rows 0..50)
%F A325165 G.f.: A(x,y) = 1 + Sum_{k>=1} x^(k^2)/((1 - y*x^k) * Product_{j=1..k-1} (1 - x^j))^2. - _Andrew Howroyd_, Jan 19 2023
%e A325165 Triangle begins:
%e A325165   1
%e A325165   0  1
%e A325165   0  0  2
%e A325165   0  0  0  3
%e A325165   0  1  0  0  4
%e A325165   0  2  0  0  0  5
%e A325165   0  3  2  0  0  0  6
%e A325165   0  4  4  0  0  0  0  7
%e A325165   0  5  6  3  0  0  0  0  8
%e A325165   0  7  8  6  0  0  0  0  0  9
%e A325165   0  9 10  9  4  0  0  0  0  0 10
%e A325165   0 13 12 12  8  0  0  0  0  0  0 11
%e A325165   0 17 16 15 12  5  0  0  0  0  0  0 12
%e A325165   0 24 20 18 16 10  0  0  0  0  0  0  0 13
%e A325165   0 31 28 21 20 15  6  0  0  0  0  0  0  0 14
%e A325165   0 42 36 27 24 20 12  0  0  0  0  0  0  0  0 15
%e A325165   0 54 50 33 28 25 18  7  0  0  0  0  0  0  0  0 16
%e A325165   0 71 64 45 32 30 24 14  0  0  0  0  0  0  0  0  0 17
%e A325165   0 90 86 57 40 35 30 21  8  0  0  0  0  0  0  0  0  0 18
%e A325165 Row n = 9 counts the following partitions (empty columns not shown):
%e A325165   (72)       (63)      (54)     (9)
%e A325165   (333)      (522)     (432)    (81)
%e A325165   (621)      (531)     (441)    (711)
%e A325165   (5211)     (4221)    (3222)   (6111)
%e A325165   (42111)    (4311)    (3321)   (51111)
%e A325165   (321111)   (32211)   (22221)  (411111)
%e A325165   (2211111)  (33111)            (3111111)
%e A325165              (222111)           (21111111)
%e A325165                                 (111111111)
%t A325165 pml[ptn_]:=If[ptn=={},{},FixedPointList[If[#=={},{},DeleteCases[Rest[#]-1,0]]&,ptn][[-3]]];
%t A325165 Table[Length[Select[IntegerPartitions[n],Total[pml[#]]==k&]],{n,0,10},{k,0,n}]
%o A325165 (PARI) T(n) = {my(v=Vec(1+sum(k=1, sqrtint(n), x^(k^2)/((1-y*x^k)*prod(j=1, k-1, 1 - x^j + O(x^(n+1-k^2))))^2))); vector(#v, i, Vecrev(v[i], -i))}
%o A325165 { my(A=T(12)); for(n=1, #A, print(A[n])) } \\ _Andrew Howroyd_, Jan 19 2023
%Y A325165 Row sums are A000041. Column k = 1 is A188674.
%Y A325165 Cf. A006918, A115720, A115994, A117485, A252464, A257990, A325163, A325166, A325168.
%K A325165 nonn,tabl
%O A325165 0,6
%A A325165 _Gus Wiseman_, Apr 05 2019