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.

A360675 Triangle read by rows where T(n,k) is the number of integer partitions of n whose right half (exclusive) sums to k, where k ranges from 0 to n.

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%I A360675 #12 Mar 11 2023 23:06:22
%S A360675 1,1,0,1,1,0,1,2,0,0,1,2,2,0,0,1,3,3,0,0,0,1,3,5,2,0,0,0,1,4,6,4,0,0,
%T A360675 0,0,1,4,9,5,3,0,0,0,0,1,5,10,10,4,0,0,0,0,0,1,5,13,12,9,2,0,0,0,0,0,
%U A360675 1,6,15,18,11,5,0,0,0,0,0,0
%N A360675 Triangle read by rows where T(n,k) is the number of integer partitions of n whose right half (exclusive) sums to k, where k ranges from 0 to n.
%C A360675 Also the number of integer partitions of n whose left half (inclusive) sums to n-k.
%e A360675 Triangle begins:
%e A360675   1
%e A360675   1  0
%e A360675   1  1  0
%e A360675   1  2  0  0
%e A360675   1  2  2  0  0
%e A360675   1  3  3  0  0  0
%e A360675   1  3  5  2  0  0  0
%e A360675   1  4  6  4  0  0  0  0
%e A360675   1  4  9  5  3  0  0  0  0
%e A360675   1  5 10 10  4  0  0  0  0  0
%e A360675   1  5 13 12  9  2  0  0  0  0  0
%e A360675   1  6 15 18 11  5  0  0  0  0  0  0
%e A360675   1  6 18 22 20  6  4  0  0  0  0  0  0
%e A360675   1  7 20 29 26 13  5  0  0  0  0  0  0  0
%e A360675   1  7 24 34 37 19 11  2  0  0  0  0  0  0  0
%e A360675   1  8 26 44 46 30 16  5  0  0  0  0  0  0  0  0
%e A360675   1  8 30 50 63 40 27  8  4  0  0  0  0  0  0  0  0
%e A360675   1  9 33 61 75 61 36 15  6  0  0  0  0  0  0  0  0  0
%e A360675   1  9 37 70 96 75 61 21 12  3  0  0  0  0  0  0  0  0  0
%e A360675 For example, row n = 9 counts the following partitions:
%e A360675   (9)  (81)   (72)     (63)       (54)
%e A360675        (441)  (432)    (333)      (3222)
%e A360675        (531)  (522)    (3321)     (21111111)
%e A360675        (621)  (4311)   (4221)     (111111111)
%e A360675        (711)  (5211)   (22221)
%e A360675               (6111)   (222111)
%e A360675               (32211)  (321111)
%e A360675               (33111)  (411111)
%e A360675               (42111)  (2211111)
%e A360675               (51111)  (3111111)
%e A360675 For example, the partition y = (3,2,2,1,1) has right half (exclusive) (1,1), with sum 2, so y is counted under T(9,2).
%t A360675 Table[Length[Select[IntegerPartitions[n], Total[Take[#,-Floor[Length[#]/2]]]==k&]],{n,0,18},{k,0,n}]
%Y A360675 The central diagonal T(2n,n) is A000005.
%Y A360675 Row sums are A000041.
%Y A360675 Diagonal sums are A360671, exclusive A360673.
%Y A360675 The right inclusive version is A360672 with rows reversed.
%Y A360675 The left version has central diagonal A360674, ranks A360953.
%Y A360675 A008284 counts partitions by length.
%Y A360675 A359893 and A359901 count partitions by median.
%Y A360675 First for prime indices, second for partitions, third for prime factors:
%Y A360675 - A360676 gives left sum (exclusive), counted by A360672, product A361200.
%Y A360675 - A360677 gives right sum (exclusive), counted by A360675, product A361201.
%Y A360675 - A360678 gives left sum (inclusive), counted by A360675, product A347043.
%Y A360675 - A360679 gives right sum (inclusive), counted by A360672, product A347044.
%Y A360675 Cf. A027193, A237363, A307683, A325347, A360005, A360071, A360254, A360616.
%K A360675 nonn,tabl
%O A360675 0,8
%A A360675 _Gus Wiseman_, Feb 27 2023