A325467 - OEIS

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A325467

Heinz numbers of integer partitions y such that the k-th differences of y are distinct (independently) for all k >= 0.

1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 102, 103, 106, 107

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OFFSET

1,2

COMMENTS

First differs from A301899 in having 70 and lacking 105.

First differs from A325398 in having 70.

First differs from A319315 in having 966.

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

The differences of a sequence are defined as if the sequence were increasing, so for example the differences of (6,3,1) are (-3,-2).

The zeroth differences of a sequence are the sequence itself, while the k-th differences for k > 0 are the differences of the (k-1)-th differences.

The enumeration of these partitions by sum is given by A325468.

LINKS

Table of n, a(n) for n=1..65.

Gus Wiseman, Sequences counting and ranking integer partitions by the differences of their successive parts.

EXAMPLE

The sequence of terms together with their prime indices begins:

1: {}

2: {1}

3: {2}

5: {3}

6: {1,2}

7: {4}

10: {1,3}

11: {5}

13: {6}

14: {1,4}

15: {2,3}

17: {7}

19: {8}

21: {2,4}

22: {1,5}

23: {9}

26: {1,6}

29: {10}

31: {11}

33: {2,5}

For example, the k-th differences for k = 0...3 of the partition (9,4,2,1) with Heinz number 966 are

9 4 2 1

-5 -2 -1

3 1

-2

and since the entries of each row are distinct, 966 belongs to the sequence.

MATHEMATICA

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

Select[Range[100], And@@Table[UnsameQ@@Differences[primeptn[#], k], {k, 0, PrimeOmega[#]}]&]

CROSSREFS

A subsequence of A005117.

Cf. A056239, A112798, A325366, A325367, A325368, A325397, A325398, A325399, A325400, A325405, A325468.

Sequence in context: A358977 A284892 A319315 * A325779 A301899 A325398

Adjacent sequences: A325464 A325465 A325466 * A325468 A325469 A325470

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 03 2019

STATUS

approved