A323306 - OEIS

A323306

Heinz numbers of integer partitions that can be arranged into a matrix with equal row-sums and equal column-sums.

1, 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 23, 25, 27, 29, 31, 32, 36, 37, 41, 43, 47, 49, 53, 59, 61, 64, 67, 71, 73, 79, 81, 83, 89, 97, 100, 101, 103, 107, 109, 113, 121, 125, 127, 128, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193

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OFFSET

1,2

COMMENTS

First differs from A137944 in lacking 120.

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).

LINKS

Table of n, a(n) for n=1..61.

Index entries for sequences related to Heinz numbers

EXAMPLE

6480 belongs to the sequence because it is the Heinz number of (3,2,2,2,2,1,1,1,1), which can be arranged in the following ways:

[1 1 3] [1 2 2] [1 2 2] [1 3 1] [2 1 2] [2 1 2] [2 2 1] [2 2 1] [3 1 1]

[2 2 1] [1 2 2] [3 1 1] [2 1 2] [1 3 1] [2 1 2] [1 1 3] [2 2 1] [1 2 2]

[2 2 1] [3 1 1] [1 2 2] [2 1 2] [2 1 2] [1 3 1] [2 2 1] [1 1 3] [1 2 2]

MATHEMATICA

primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];

facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];

ptnmats[n_]:=Union@@Permutations/@Select[Union@@(Tuples[Permutations/@#]&/@Map[primeMS, facs[n], {2}]), SameQ@@Length/@#&];

Select[Range[100], !Select[ptnmats[#], And[SameQ@@Total/@#, SameQ@@Total/@Transpose[#]]&]=={}&]

CROSSREFS

Complement of A323304.

Cf. A006052, A007016, A056239, A112798, A120733, A319056, A319066, A321719.

Cf. A323300, A323302, A323347, A323348, A323349.

Sequence in context: A046686 A137944 A359390 * A325247 A306013 A268082

Adjacent sequences: A323303 A323304 A323305 * A323307 A323308 A323309

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 13 2019

STATUS

approved