A330667 - OEIS

A330667

Irregular triangle read by rows where T(n,k) is the number of balanced reduced multisystems of depth k whose atoms are the prime indices of n.

1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 2, 0, 1, 1, 0, 1, 0, 1, 3, 2, 0, 1, 1, 2, 0, 1, 1, 2, 0, 1, 0, 1, 0, 1, 1, 5, 5, 0, 1, 0, 1, 0, 1, 1, 0, 1, 2, 0, 1, 1, 3, 0, 1, 1, 5, 9, 5, 0, 1, 0, 1, 0, 1, 0, 1, 7, 7, 0, 1, 1, 0, 1, 0, 1, 5, 5, 0, 1, 1, 3

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OFFSET

1,18

COMMENTS

A balanced reduced multisystem is either a finite multiset, or a multiset partition with at least two parts, not all of which are singletons, of a balanced reduced multisystem.

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.

LINKS

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

EXAMPLE

Triangle begins:

{}

1 0

1 1 0

1 0

1 2 0

1 0

1 3 2 0

1 2 0

Row n = 84 counts the following multisystems (commas elided):

{1124} {{1}{124}} {{{1}}{{1}{24}}}

{{11}{24}} {{{11}}{{2}{4}}}

{{12}{14}} {{{1}}{{2}{14}}}

{{2}{114}} {{{12}}{{1}{4}}}

{{4}{112}} {{{1}}{{4}{12}}}

{{1}{1}{24}} {{{14}}{{1}{2}}}

{{1}{2}{14}} {{{2}}{{1}{14}}}

{{1}{4}{12}} {{{2}}{{4}{11}}}

{{2}{4}{11}} {{{24}}{{1}{1}}}

{{{4}}{{1}{12}}}

{{{4}}{{2}{11}}}

MATHEMATICA

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

totfac[n_, k_]:=If[k==1, 1, Sum[totfac[Times@@Prime/@f, k-1], {f, Select[facs[n], 1<Length[#]<PrimeOmega[n]&]}]];

Table[totfac[n, k], {n, 100}, {k, PrimeOmega[n]}]

CROSSREFS

Row lengths are A001222.

Row sums are A318812.

The last nonzero term of row n is A330665(n).

Column k = 2 is 0 if n is prime; otherwise it is A001055(n) - 2.

Cf. A000311, A000669, A001678, A005121, A008827, A213427, A317145, A318846, A330474, A330475, A330655, A330666.

Sequence in context: A033778 A091586 A363037 * A116377 A131964 A356241

Adjacent sequences: A330664 A330665 A330666 * A330668 A330669 A330670

KEYWORD

nonn,tabf

AUTHOR

Gus Wiseman, Dec 27 2019

STATUS

approved