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A329554 Smallest MM-number of a set of n nonempty sets with no singletons. 5
1, 13, 377, 16211, 761917, 55619941, 4393975339, 443791509239, 50148440544007, 6870336354528959, 954976753279525301, 142291536238649269849, 23193520406899830985387, 3873317907952271774559629, 701070541339361191195292849, 139513037726532877047863276951 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

A multiset multisystem is a finite multiset of finite multisets. 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 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 multisystem with MM-number 78 is {{},{1},{1,2}}.

LINKS

Table of n, a(n) for n=0..15.

FORMULA

a(n) = Product_{i = 1..n} prime(A120944(i)).

EXAMPLE

The sequence of terms together with their corresponding systems begins:

       1: {}

      13: {{1,2}}

     377: {{1,2},{1,3}}

   16211: {{1,2},{1,3},{1,4}}

  761917: {{1,2},{1,3},{1,4},{2,3}}

MATHEMATICA

sqvs=Select[Range[2, 30], SquareFreeQ[#]&&!PrimeQ[#]&];

Table[Times@@Prime/@Take[sqvs, k], {k, 0, Length[sqvs]}]

CROSSREFS

The smallest BII-number of a set of n sets is A000225(n).

BII-numbers of set-systems with no singletons are A326781.

MM-numbers of sets of nonempty sets are the odd terms of A302494.

MM-numbers of multisets of nonempty non-singleton sets are A320629.

The version with empty edges is A329556.

The version with singletons is A329557.

The version with empty edges and singletons is A329558.

Cf. A056239, A072639, A112798, A279952, A302242, A326031, A329552, A329556.

Classes of MM-numbers: A305078 (connected), A316476 (antichains), A318991 (chains), A320456 (covers), A329559 (clutters).

Sequence in context: A320635 A279306 A134498 * A267433 A142122 A302700

Adjacent sequences:  A329551 A329552 A329553 * A329555 A329556 A329557

KEYWORD

nonn

AUTHOR

Gus Wiseman, Nov 17 2019

STATUS

approved

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Last modified September 18 00:01 EDT 2021. Contains 347489 sequences. (Running on oeis4.)