A330098 - OEIS

A330098

Number of distinct multisets of multisets that can be obtained by permuting the vertices of the multiset of multisets with MM-number n.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2

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OFFSET

1,35

COMMENTS

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 of multisets with MM-number n is formed by taking the multiset of prime indices of each part of the multiset of prime indices of n. For example, the prime indices of 78 are {1,2,6}, so the multiset of multisets with MM-number 78 is {{},{1},{1,2}}.

a(n) is a divisor of A303975(n)!.

LINKS

Table of n, a(n) for n=1..87.

EXAMPLE

The vertex-permutations of {{1,2},{2,3,3}} are:

{{1,2},{1,3,3}}

{{1,2},{2,3,3}}

{{1,3},{1,2,2}}

{{1,3},{2,2,3}}

{{2,3},{1,1,2}}

{{2,3},{1,1,3}}

so a(4927) = 6.

MATHEMATICA

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

graprms[m_]:=Union[Table[Sort[Sort/@(m/.Rule@@@Table[{p[[i]], i}, {i, Length[p]}])], {p, Permutations[Union@@m]}]];

Table[Length[graprms[primeMS/@primeMS[n]]], {n, 100}]

CROSSREFS

Positions of 1's are A330232.

Positions of first appearances are A330230 and A330233.

The BII-number version is A330231.

Cf. A001055, A003238, A007716, A055621, A056239, A112798, A302242, A303975, A322847, A330194, A330218, A330223, A330227, A330236.

Sequence in context: A334377 A063053 A063050 * A189024 A304720 A057557

Adjacent sequences: A330095 A330096 A330097 * A330099 A330100 A330101

KEYWORD

nonn

AUTHOR

Gus Wiseman, Dec 09 2019

STATUS

approved