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.

A344651 Irregular triangle read by rows where T(n,k) is the number of integer partitions of n with alternating sum k, with k ranging from n mod 2 to n in steps of 2.

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%I A344651 #12 Dec 10 2021 11:11:12
%S A344651 1,1,1,1,2,1,2,2,1,4,2,1,3,5,2,1,7,5,2,1,5,9,5,2,1,12,10,5,2,1,7,17,
%T A344651 10,5,2,1,19,19,10,5,2,1,11,28,20,10,5,2,1,30,33,20,10,5,2,1,15,47,35,
%U A344651 20,10,5,2,1,45,57,36,20,10,5,2,1,22,73,62,36,20,10,5,2,1
%N A344651 Irregular triangle read by rows where T(n,k) is the number of integer partitions of n with alternating sum k, with k ranging from n mod 2 to n in steps of 2.
%C A344651 The alternating sum of a partition (y_1,...,y_k) is Sum_i (-1)^(i-1) y_i. This is equal to the number of odd parts in the conjugate partition, so T(n,k) is the number of integer partitions of n with k odd parts in the conjugate partition, which is also the number of partitions of n with k odd parts.
%C A344651 Also the number of integer partitions of n with odd-indexed parts (odd bisection) summing to k, ceiling(n/2) <= k <= n. The even-indexed version is A346633. - _Gus Wiseman_, Nov 29 2021
%e A344651 Triangle begins:
%e A344651    1
%e A344651    1
%e A344651    1   1
%e A344651    2   1
%e A344651    2   2   1
%e A344651    4   2   1
%e A344651    3   5   2   1
%e A344651    7   5   2   1
%e A344651    5   9   5   2   1
%e A344651   12  10   5   2   1
%e A344651    7  17  10   5   2   1
%e A344651   19  19  10   5   2   1
%e A344651   11  28  20  10   5   2   1
%e A344651   30  33  20  10   5   2   1
%e A344651   15  47  35  20  10   5   2   1
%e A344651   45  57  36  20  10   5   2   1
%e A344651   22  73  62  36  20  10   5   2   1
%e A344651   67  92  64  36  20  10   5   2   1
%e A344651   30 114 102  65  36  20  10   5   2   1
%e A344651   97 147 107  65  36  20  10   5   2   1
%e A344651 Row n = 10 counts the following partitions (A = 10):
%e A344651   (55)          (64)         (73)       (82)     (91)   (A)
%e A344651   (3322)        (442)        (433)      (622)    (811)
%e A344651   (4411)        (541)        (532)      (721)
%e A344651   (222211)      (3331)       (631)      (7111)
%e A344651   (331111)      (4222)       (5221)     (61111)
%e A344651   (22111111)    (4321)       (6211)
%e A344651   (1111111111)  (5311)       (42211)
%e A344651                 (22222)      (52111)
%e A344651                 (32221)      (511111)
%e A344651                 (33211)      (4111111)
%e A344651                 (43111)
%e A344651                 (322111)
%e A344651                 (421111)
%e A344651                 (2221111)
%e A344651                 (3211111)
%e A344651                 (31111111)
%e A344651                 (211111111)
%e A344651 The conjugate version is:
%e A344651   (A)      (55)      (3331)     (331111)    (31111111)   (1111111111)
%e A344651   (64)     (73)      (5311)     (511111)    (211111111)
%e A344651   (82)     (91)      (7111)     (3211111)
%e A344651   (442)    (433)     (33211)    (4111111)
%e A344651   (622)    (532)     (43111)    (22111111)
%e A344651   (4222)   (541)     (52111)
%e A344651   (22222)  (631)     (61111)
%e A344651            (721)     (322111)
%e A344651            (811)     (421111)
%e A344651            (3322)    (2221111)
%e A344651            (4321)
%e A344651            (4411)
%e A344651            (5221)
%e A344651            (6211)
%e A344651            (32221)
%e A344651            (42211)
%e A344651            (222211)
%t A344651 ats[y_]:=Sum[(-1)^(i-1)*y[[i]],{i,Length[y]}];
%t A344651 Table[Length[Select[IntegerPartitions[n],ats[#]==k&]],{n,0,15},{k,Mod[n,2],n,2}]
%Y A344651 This is A103919 with all zeros removed.
%Y A344651 The strict version is A152146 interleaved with A152157.
%Y A344651 The rows are those of A239830 interleaved with those of A239829.
%Y A344651 The reverse version is the right half of A344612.
%Y A344651 The strict reverse version is the right half of A344739.
%Y A344651 A000041 counts partitions of 2n with alternating sum 0, ranked by A000290.
%Y A344651 A027187 counts partitions with rev-alternating sum <= 0, ranked by A028260.
%Y A344651 A124754 lists alternating sums of standard compositions (reverse: A344618).
%Y A344651 A316524 is the alternating sum of the prime indices of n (reverse: A344616).
%Y A344651 A325534/A325535 count separable/inseparable partitions.
%Y A344651 A344607 counts partitions with rev-alternating sum >= 0, ranked by A344609.
%Y A344651 A344608 counts partitions with rev-alternating sum < 0, ranked by A119899.
%Y A344651 A344610 counts partitions of n by positive rev-alternating sum.
%Y A344651 A344611 counts partitions of 2n with rev-alternating sum >= 0.
%Y A344651 A345197 counts compositions by sum, length, and alternating sum.
%Y A344651 A346697 gives the sum of odd-indexed prime indices (reverse: A346699).
%Y A344651 A346702 represents the odd bisection of compositions, sums A209281.
%Y A344651 Cf. A000070, A000097, A003242, A006330, A025047, A097805, A114121, A116406, A131577, A344617, A344649, A344650, A344654, A346633.
%K A344651 nonn,tabf
%O A344651 0,5
%A A344651 _Gus Wiseman_, Jun 05 2021