A363219 - OEIS

A363219

Twice the median of the conjugate of the integer partition with Heinz number n.

0, 2, 2, 4, 2, 3, 2, 6, 4, 2, 2, 4, 2, 2, 4, 8, 2, 5, 2, 2, 3, 2, 2, 5, 4, 2, 6, 2, 2, 4, 2, 10, 2, 2, 4, 6, 2, 2, 2, 2, 2, 3, 2, 2, 6, 2, 2, 6, 4, 4, 2, 2, 2, 7, 4, 2, 2, 2, 2, 4, 2, 2, 4, 12, 3, 2, 2, 2, 2, 4, 2, 7, 2, 2, 6, 2, 4, 2, 2, 2, 8, 2, 2, 3, 2, 2

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OFFSET

1,2

COMMENTS

The median of a multiset is either the middle part (for odd length), or the average of the two middle parts (for even length). Since the denominator is always 1 or 2, the median can be represented as an integer by multiplying by 2.

The Heinz number of a partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k). This gives a bijective correspondence between positive integers and integer partitions.

LINKS

Table of n, a(n) for n=1..86.

EXAMPLE

The partition (4,2,1) has Heinz number 42 and conjugate (3,2,1,1) with median 3/2, so a(42) = 3.

MATHEMATICA

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

conj[y_]:=If[Length[y]==0, y, Table[Length[Select[y, #>=k&]], {k, 1, Max[y]}]];

Table[If[n==1, 0, 2*Median[conj[prix[n]]]], {n, 100}]

CROSSREFS

Twice the row media of A321649 or A321650.

For mean instead of twice median we have A326839/A326840.

This is the conjugate version of A360005.

A000700 counts self-conjugate partitions, ranked by A088902 (cf. A258116).

A056239 adds up prime indices, row sums of A112798 and A296150.

A122111 is partition conjugation in terms of Heinz numbers.

A124010 gives prime signature, sorted A118914, length A001221, sum A001222.

A352491 gives n minus Heinz number of conjugate.

A363220 counts partitions with same median as conjugate.

Cf. A046682, A321648, A325040, A326567/A326568, A326848, A362617, A362618, A363223, A363224.

Sequence in context: A332581 A328059 A123674 * A371531 A238745 A092607

Adjacent sequences: A363216 A363217 A363218 * A363220 A363221 A363222

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 25 2023

STATUS

approved