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A326536 MM-numbers of multiset partitions where every part has the same average. 9
1, 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 21, 23, 25, 27, 29, 31, 32, 37, 41, 43, 47, 49, 53, 57, 59, 61, 63, 64, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109, 113, 115, 121, 125, 127, 128, 131, 133, 137, 139, 145, 147, 149, 151, 157, 159, 163, 167 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

First differs from A322902 in having 145.

These are numbers where each prime index has the same average of prime indices. A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. The multiset multisystem with MM-number n is obtained by taking the multiset of prime indices of each prime index of n. For example, the prime indices of 78 are {1,2,6}, so the multiset multisystem with MM-number 78 is {{},{1},{1,2}}.

LINKS

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

Gus Wiseman, Sequences counting and ranking multiset partitions whose part lengths, sums, or averages are constant or strict.

EXAMPLE

The sequence of multiset partitions where every part has the same average, preceded by their MM-numbers, begins:

   1: {}

   2: {{}}

   3: {{1}}

   4: {{},{}}

   5: {{2}}

   7: {{1,1}}

   8: {{},{},{}}

   9: {{1},{1}}

  11: {{3}}

  13: {{1,2}}

  16: {{},{},{},{}}

  17: {{4}}

  19: {{1,1,1}}

  21: {{1},{1,1}}

  23: {{2,2}}

  25: {{2},{2}}

  27: {{1},{1},{1}}

  29: {{1,3}}

  31: {{5}}

  32: {{},{},{},{},{}}

MATHEMATICA

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

Select[Range[100], SameQ@@Mean/@primeMS/@primeMS[#]&]

CROSSREFS

Cf. A038041, A051293, A112798, A302242, A320324, A326512, A326515, A326520, A326533, A326534, A326535, A326537.

Sequence in context: A014567 A324769 A328867 * A322902 A302040 A302036

Adjacent sequences:  A326533 A326534 A326535 * A326537 A326538 A326539

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jul 12 2019

STATUS

approved

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Last modified February 23 16:22 EST 2020. Contains 332177 sequences. (Running on oeis4.)